Display device, display method and machine readable storage medium

ABSTRACT

In a display method or device according to one embodiment of the present invention, at least two of a photonic crystal reflection mode, a unique color reflection mode and a transmittance tuning mode may be implemented to be switched to each other within the same unit pixel. In addition, a machine readable storage medium recording a computer program performing the display method is provided.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a display method and device. Moreparticularly, the present invention relates to a display method anddevice implemented so as to switch at least two of a photonic crystalreflection mode, a unique color reflection mode and a transmittancetuning mode to each other within the same pixel.

2. Description of the Related Art

Recently, as the research and development of next-generation displays isactively being pursued, a variety of displays is being introduced. Atypical example of the next-generation displays may include anelectronic ink. The electronic ink is a display in which an electricfield is applied to particles of specific colors (e.g., black and white)respectively having negative charges and positive charges to display thespecific colors. Electronic ink has the advantages of low powerconsumption and flexible display. However, the electronic ink is limitedbecause it is difficult to represent various colors since the color ofthe particles is set to specific colors. Meanwhile, it has beenintroduced a light transmittance tuning device that is used togetherwith a display so as to serve to transmit or block light reflected fromthe display or incident on the display. The light transmittance tuningdevice according to the related art includes a mechanical shutterperforming a function of tuning light transmission, etc., and as aresult, has a complicated structure and too much manufacturing time andmanufacturing costs are required.

Therefore, a need exists to tune various hues and/or transmittance in adisplay region by a simple method while simplifying the structure.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a display method anddevice capable of implementing various hues and/or transmittance withinthe same pixel by a simple method and structure.

Another object of the present invention is to provide a display methodand device capable of tuning various hues, transmittance, brightnessand/or chroma by a simple method and structure.

Still another object of the present invention is to provide a displaymethod and device capable of improving intensity of a light wavelengthreflected from particles by more regularly arranging inter-particledistances.

Still yet another object of the present invention is to provide amachine readable storage medium on which a program code executingprocesses of the display method is recorded.

According to an embodiment of the present invention, there is provided adisplay method applying an electric field through an electrode to adisplay unit including a solution, in which particles are dispersed inthe solvent, and controlling at least one of the intensity, direction,application frequency, application time and application location of theelectric field to control at least one of the interval, location andarrangement of the particles, wherein the display method is implementedto selectively switch, within a same pixel of the display unit, betweena first mode for controlling a wavelength of light reflected from theparticles whose distances are controlled by controlling inter-particledistances; and a second mode for displaying at least one color of theparticles, the solvent, the solution and the electrode by controllingthe location of the particles.

According to another embodiment of the present invention, there isprovided a display method applying an electric field through anelectrode to a display unit including a solution, in which particles aredispersed in the solvent, and controlling at least one of the intensity,direction, application frequency, application time and applicationlocation of the electric field to control at least one of the interval,location and arrangement of the particles, wherein the display method isimplemented to selectively switch, within a same pixel of the displayunit, between a first mode for controlling a wavelength of lightreflected from the particles whose distances are controlled bycontrolling inter-particle distances; and a second mode for tuningtransmittance of light transmitting the solution by controlling thedistance, location or arrangement of the particles.

According to another embodiment of the present invention, there isprovided a display method applying an electric field through anelectrode to a display unit including a solution, in which particles aredispersed in the solvent, and controlling at least one of the intensity,direction, application frequency, application time and applicationlocation of the electric field to control at least one of the interval,location and arrangement of the particles, wherein the display method isimplemented to selectively switch, within a same pixel of the displayunit, between a first mode for displaying at least one color of theparticles, the solvent, the solution and the electrode by controllingthe location of the particles; and a second mode for tuningtransmittance of light transmitting the solution by controlling thedistance, location or arrangement of the particles.

According to another embodiment of the present invention, there isprovided a display method applying an electric field through anelectrode to a display unit including a solution, in which particles aredispersed in the solvent, and controlling at least one of the intensity,direction, application frequency, application time and applicationlocation of the electric field to control at least one of the interval,location and arrangement of the particles, wherein the display method isimplemented to selectively switch, within a same pixel of the displayunit, between a first mode for controlling a wavelength of lightreflected from the particles whose distances are controlled bycontrolling the location of the particles; a second mode for displayingat least one color of the particles, the solvent, the solution and theelectrode by controlling the location of the particles; and a third modefor tuning transmittance of light transmitting the solution bycontrolling the distance, location or arrangement of the particles.

According to another embodiment of the present invention, there isprovided a display device, including: a display unit including asolution in which particles between two electrodes opposite to eachother are dispersed in the solvent, at least one of the two electrodesbeing transparent; and a control unit for controlling at least one ofthe intensity, direction, application frequency, application time andapplication location of an electric field applied to the electrodes tocontrol at least one of the interval, location and arrangement of theparticles, wherein the control unit is implemented to selectivelyswitch, within a same pixel of the display, between a first mode forcontrolling a wavelength of light reflected from the particles whosedistances are controlled by controlling inter-particle distances; and asecond mode for displaying at least one color of the particles, thesolvent, the solution and the electrode by controlling the location ofthe particles.

According to another embodiment of the present invention, there isprovided a display device including: a display unit including a solutionin which particles between two electrodes opposite to each other aredispersed in the solvent, at least one of the two electrodes beingtransparent; and a control unit for controlling at least one of theintensity, direction, application frequency, application time andapplication location of an electric field applied to the electrode tocontrol at least one of the interval, location and arrangement of theparticles, wherein the control unit is implemented to selectivelyswitch, within a same unit pixel of a display unit, between a first modefor controlling a wavelength of light reflected from the particles whosedistances are controlled by controlling inter-particle distances; and asecond mode for tuning transmittance of light transmitting the solutionby controlling the distance, location or arrangement of the particles.

According to another embodiment of the present invention, there isprovided a display device including: a display unit including a solutionin which particles between two electrodes opposite to each other aredispersed in the solvent, at least one of the two electrodes beingtransparent; and a control unit for controlling at least one of theintensity, direction, application frequency, application time andapplication location of the electric field to control at least one ofthe interval, location and arrangement of the particles, the controlunit is implemented to selectively switch, within a same unit pixel of adisplay unit, between a first mode for displaying at least one color ofthe particles, the solvent, the solution and the electrode bycontrolling the location of the particles; and a second mode for tuningtransmittance of light transmitting the solution by controlling thedistance, location or arrangement of the particles.

According to another embodiment of the present invention, there isprovided a display device, including: a display unit including asolution in which particles between two electrodes opposite to eachother are dispersed in the solvent, at least one of the two electrodesbeing transparent; and a control unit for controlling at least one ofthe intensity, direction, application frequency, application time andapplication location of an electric field applied to the electrode tocontrol at least one of the interval, location and arrangement of theparticles, wherein the control unit is implemented to selectivelyswitch, within a same unit pixel of a display unit, between a first modefor controlling a wavelength of light reflected from the particles whosedistances are controlled by controlling inter-particle distances; asecond mode for displaying at least one color of the particles, thesolvent, the solution and the electrode by controlling the location ofthe particles; and a third mode for tuning the transmittance of lighttransmitting the solution by controlling the distance, location orarrangement of the particles.

According to another embodiment of the present invention, there isprovided a machine readable storage medium stored with a program coderead by a machine and applying an electric field through an electrode toa display unit including a solution in which particles are dispersed inthe solvent and controlling at least one of the intensity, direction,application frequency, application time and application location of theelectric field to control at least one of the interval, location andarrangement of the particles, wherein the program code is implemented toselectively switch, within a same unit pixel of a display unit, betweena first mode for controlling a wavelength of light reflected from theparticles whose distances are controlled by controlling inter-particledistances; and a second mode for displaying at least one color of theparticles, the solvent, the solution and the electrode by controllingthe location of the particles.

According to another embodiment of the present invention, there isprovided a machine readable storage medium stored with a program coderead by a machine and applying an electric field through an electrode toa display unit including a solution in which particles are dispersed inthe solvent and controlling at least one of the intensity, direction,application frequency, application time and application location of theelectric field to control at least one of the interval, location andarrangement of the particles, wherein the program code is implemented toselectively switch, within a same unit pixel of a display unit, betweena first mode for controlling a wavelength of light reflected from theparticles whose distances are controlled by controlling inter-particledistances; and a second mode for tuning transmittance of lighttransmitting the solution by controlling the distance, location orarrangement of the particles.

According to another embodiment of the present invention, there isprovided a machine readable storage medium stored with a program coderead by a machine and applying an electric field through an electrode toa display unit including a solution in which particles are dispersed inthe solvent and controlling at least one of the intensity, direction,application frequency, application time and application location of theelectric field to control at least one of the interval, location andarrangement of the particles, wherein the program code is implemented toselectively switch, within a same unit pixel of a display unit, betweena first mode for displaying at least one color of the particles, thesolvent, the solution and the electrode by controlling the location ofthe particles; and a second mode for tuning transmittance of lighttransmitting the solution by controlling the distance, location orarrangement of the particles.

According to another embodiment of the present invention, there isprovided a machine readable storage medium stored with a program coderead by a machine and applying an electric field through an electrode toa display unit including a solution in which particles are dispersed inthe solvent and controlling at least one of the intensity, direction,application frequency, application time and application location of theelectric field to control at least one of the interval, location andarrangement of the particles, wherein the program code is implemented toselectively switch, within a same unit pixel of a display unit, betweena first mode for controlling a wavelength of light reflected from theparticles whose distances are controlled by controlling inter-particledistances; a second mode for displaying at least one color of theparticles, the solvent, the solution and the electrode by controllingthe location of the particles; and a third mode for tuning transmittanceof light transmitting the solution by controlling the distance, locationor arrangement of the particles.

Each of the following embodiments may be applied to all of the displaymethod, the display device and the storage medium.

In one embodiment, the switching between the modes may be performed bychanging at least one of the intensity, direction, application frequencyand application location of the electric field.

In one embodiment, DC electric field and AC electric field may be mixedsequentially or simultaneously and applied.

In one embodiment, the electrode may be divided into a large electrodeand a local electrode so as to be electrically isolated from each other.

In one embodiment, in order to control the location of the particles,the particles charged with electric charges of a same sign may be used.

In one embodiment, in order to control the location of the particles,the particles having different dielectric constant from the solvent isused and a non-uniform electric field may be applied to the displayunit.

In one embodiment, in order to tune the transmittance of light, awavelength of light reflected from the particles may be controlledbeyond a visible spectrum.

In one embodiment, in order to tune the transmittance of light, theparticles charged with electric charges of a same sign is used and theelectric field is locally applied to the display unit, and thus, theparticles are locally moved by electrophoresis.

In one embodiment, in order to tune the transmittance of light, theparticles having different dielectric constant from the solvent is usedand a non-uniform electric field is applied to the display unit.

In one embodiment, the particles may be arranged in a direction parallelto the direction of the electric field by electrorheology to tune thetransmittance.

In one embodiment, at least one of the particles, solvent and solutionhas a variable electrical polarization characteristic, which is acharacteristic that an amount of electrical polarization inducedaccording to the change of the applied electric field is changed.

In one embodiment, at least one of the particles, the solvent and thesolution may be electrically polarized by at least one of electronicpolarization, ionic polarization, interfacial polarization androtational polarization.

In one embodiment, the solvent may be a material including apolarization index of 1 or more.

In one embodiment, the solvent may include propylene carbonate.

In one embodiment, the particles may include a ferroelectric orsuperparaelectric material.

In one embodiment, the particles may include inorganic compoundsincluding at least one of Ti, Zr, Ba, Si, Au, Ag, Fe, Ni and Co ororganic compounds including carbon.

In one embodiment, the particles may have the electric charges of a samesign, and as the electric field is applied, the inter-particle distancesmay be reached within the specific range by mutually applyingelectrophoresis force acting to the particles proportional to theintensity of electric field, electrostatic attraction acting between theparticles by the variable electrical polarization characteristic andelectrostatic repulsion acting between the particles having the electriccharges of the same sign act mutually so that the inter-particledistances are reached within a specific range, and thus, light having aspecific wavelength is reflected from the particles.

In one embodiment, the particles may show a mutual steric effect, and asthe electric field is applied, the electrostatic attraction actingbetween the particles by the variable electrical polarizationcharacteristic and steric hindrance repulsion acting between theparticles may acts on each other so that the inter-particle distancesare reached within a specific range, and thus, light having a specificwavelength is reflected from particles.

In one embodiment, when the electric field is applied, the particles maybe arranged within the solvent with having a three-dimensional shortrange ordering.

In one embodiment, the wavelength of light reflected from the particlesmay become short as the intensity of the electric field is increased.

In one embodiment, a possible wavelength range of light reflected fromthe particles may be at least one of infrared, visible and ultravioletspectrums.

In one embodiment, at least one of the particles, the solvent and theelectrode may have at least one component of materials having pigments,dyes and structural colors.

In one embodiment, each of a plurality of pixels may be independentlydriven by independently applying the electric field to each of theplurality of pixels.

In one embodiment, the particles and solvent may be encapsulated by alight transmissive material or may be partitioned by an insulatingmaterial.

In one embodiment, the particles and solvent may be dispersed in amedium made of a light transmissive material.

In one embodiment, the solution may be a gel type.

In one embodiment, although the electric field is removed after aspecific color or transmittance is displayed by applying the electricfield to the solution, the specific color or transmittance is maintainedfor a predetermined time.

In one embodiment, a unit pixel, in which the switching between themodes is performed, is vertically stacked in a plural number and themodes may be independently implemented within each stacked unit pixel.

In one embodiment, a unit pixel, in which the switching between themodes is performed, may be horizontally arranged in a plural number andthe modes may be independently implemented within each arranged unitpixel.

In one embodiment, the electric field is applied to the particles or thesolvent, and then, the interval, location or arrangement may be reset byapplying the electric field in an opposite direction to the electricfield.

In one embodiment, the display method may further include prior toapplying the electric field, applying standby electric field so as tomaintain the distance, location or arrangement of the particles to bepreviously set interval, location or arrangement.

In one embodiment, a capacitor is connected to the display unit, so thatelectric charges may be charged in the capacitor when the voltage isapplied, when the voltage applied to the display unit is blocked,voltage may be applied to the display unit using the electric chargescharged in the capacitor.

In one embodiment, it may control brightness or chroma of a colordisplayed by controlling at least one of a display area, display timeand transmittance of light.

In one embodiment, the electric field is applied to first and secondparticles having electric charges of different signs so that thedistance, location or arrangement of first particles and the distance,location or arrangement of second particles may be independentlycontrolled.

In one embodiment, energy may be generated using light incident to theparticles and the solvent, and the electric field may be applied byusing the generated energy.

In one embodiment, an emissive display means is used to implement themode or the emissive display means is used by being combined with themode.

In one embodiment, the light reflected from the particles, the solvent,or the electrode or the light transmitting the particles, the solvent,or the electrode may be displayed through a color filter connected tothe electrode.

In one embodiment, the particles and the electrode may each be white andblack or may each be black and white.

In one embodiment, the mode for controlling the wavelength of lightreflected by controlling the inter-particle distances may have amagnitude in the applied voltage smaller than that of the mode fortuning the transmittance of light by controlling the arrangement of theparticles.

In one embodiment, as the applied voltage becomes larger, inter-particleattraction by a variable electrical polarization characteristic maybecome large so that inter-particle repulsion may be disregarded.

In one embodiment, the arrangement of the particles is controlled sothat inter-particle attraction by the variable electrical polarizationcharacteristic may become larger than the inter-particle repulsion inthe mode for tuning the transmittance of light.

In one embodiment, the transmittance may be varied continuously or in ananalog method.

As set forth above, the embodiments of the present invention canimplement various hues or continuous hues and/or transmittance withinthe same unit pixel by the simple structure.

In addition, the embodiments of the present invention can controlvarious hues, transmittance, chroma and/or brightness by the simplestructure.

Further, the embodiments of the present invention can implement the huesof the continuous wavelength by reflecting the light of the continuouswavelength rather than implementing the hues by the mixing of R, G andB.

Also, the display method in accordance with one embodiment of thepresent invention can simultaneously satisfy the large area display, thesimple display method, the continuous hue implementation, the use in theflexible display region and the display of the low power consumption.

Moreover, the embodiments of the present invention can provide thedisplay method and device having the excellent viewing anglecharacteristic and response time.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention willbecome apparent from the following description of the preferredembodiments, given in conjunction with the accompanying drawings, inwhich:

FIGS. 1 and 2 are views illustrating the configuration of particlescontained in a display device in accordance with one embodiment of thepresent invention;

FIG. 3 is a view illustrating the configuration of polarization ofparticles or solvent upon application of an electric field in accordancewith one embodiment of the present invention;

FIG. 4 is a view illustrating unit polarization characteristic exhibitedby the asymmetrical arrangement of molecule in accordance with oneembodiment of the present invention;

FIG. 5 is a view illustrating hysteresis curves of a paraelectricmaterial, a ferroelectric material and a superparaelectric material;

FIG. 6 is a view illustrating a material having a perovskite structurethat may be included in the particles or the solvent in accordance withone embodiment of the present invention;

FIG. 7 is a view conceptually illustrating a configuration ofcontrolling inter-particle distances in accordance with a firstembodiment of a first mode of a display device of the present invention;

FIG. 8 is a view conceptually illustrating a configuration ofcontrolling inter-particle distances in accordance with a secondembodiment of the first mode of the display device of the presentinvention;

FIGS. 9 and 10 each are views conceptually illustrating theconfiguration of the display device accordance with the first and secondembodiments of the first mode of the display device of the presentinvention;

FIG. 11 is a view exemplarily illustrating the configuration of thefirst mode in accordance with one embodiment of the present invention;

FIG. 12 is a view exemplarily illustrating a configuration of a secondmode of the display device in accordance with one embodiment of thepresent invention;

FIG. 13 is a view exemplarily illustrating the configuration of thesecond mode of the display device in accordance with one embodiment ofthe present invention;

FIG. 14 is a view exemplarily illustrating a configuration of a thirdmode of the display device in accordance with one embodiment of thepresent invention;

FIG. 15 is a view exemplary illustrating the configuration of thedisplay device capable of selectively performing the first and secondmodes in accordance with one embodiment of the present invention;

FIG. 16 is a view exemplarily illustrating the configuration of thedisplay device capable of selectively performing the first mode and athird mode in accordance with one embodiment of the present invention;

FIG. 17 is a view exemplarily illustrating the configuration of thedisplay device capable of selectively performing the second and thirdmodes in accordance with one embodiment of the present invention;

FIG. 18 is a view exemplarily illustrating the configuration of thedisplay device capable of selectively performing the first, second andthird modes in accordance with one embodiment of the present invention;

FIG. 19 is a view exemplarily illustrating the configuration of thedisplay device driven by a plurality of electrodes in accordance withone embodiment of the present invention;

FIG. 20 is a view illustrating a configuration in which the particlesand solvent included in the display device are encapsulated in aplurality of capsules in accordance with one embodiment of the presentinvention;

FIG. 21 is a view illustrating a configuration in which particles andsolvent included in the display device are dispersed in a medium inaccordance with one embodiment of the present invention;

FIG. 22 is a view exemplarily illustrating the composition of a solutionencapsulated with a light transmissive medium in accordance with oneembodiment of the present invention;

FIG. 23 is a view illustrating the composition of the particles andsolvent dispersed in a medium in accordance with one embodiment of thepresent invention;

FIG. 24 is a view illustrating a configuration in which the particlesand solvent included in the display device are partitioned into aplurality of cells in accordance with one embodiment of the presentinvention;

FIGS. 25 and 26 are views exemplarily illustrating a configuration inwhich the display device in accordance with one embodiment of thepresent invention is combined with each other in a vertical direction ora horizontal direction;

FIGS. 27 to 29 are views illustrating a pattern of voltages applied tothe display device in accordance with one embodiment of the presentinvention;

FIG. 30 is a view exemplarily illustrating a configuration of a circuitconnected to a plurality of electrodes of the display device inaccordance with one embodiment of the present invention;

FIG. 31 is a view exemplarily illustrating a configuration ofcontrolling a display area of light reflected from particles inaccordance with one embodiment of the present invention;

FIG. 32 is a view exemplarily illustrating a configuration ofcontrolling a display time of light reflected from particles inaccordance with one embodiment of the present invention;

FIG. 33 is a view exemplarily illustrating a configuration ofcontrolling brightness using a light tuning layer in accordance with oneembodiment of the present invention;

FIGS. 34 and 35 are views exemplarily illustrating a configuration ofthe light tuning layer tuning transmittance of light in accordance withone embodiment of the present invention;

FIG. 36 is a view exemplarily illustrating a configuration of the lighttuning layer controlling a light blocking rate in accordance with oneembodiment of the present invention;

FIG. 37 is a view illustrating the configuration of a display device forrealizing a photonic crystal display using particles having differentelectric charges from each other in accordance with one embodiment ofthe present invention;

FIGS. 38 to 40 are views exemplarily illustrating a configuration ofpatterning an electrode in accordance with one embodiment of the presentinvention;

FIG. 41 is a view exemplarily illustrating the configuration in whichthe display device in accordance with one embodiment of the presentinvention includes a spacer;

FIG. 42 is a view illustrating the configuration of a display deviceincluding a solar cell unit in accordance with one embodiment of thepresent invention;

FIG. 43 is a view exemplarily illustrating a configuration in which thedisplay device in accordance with the present invention is combined withan emissive display device;

FIGS. 44 to 46 are graphs and photographs illustrating experimentalresults implementing the first mode for controlling the wavelength oflight reflected photonic crystals composed of the particles bycontrolling the inter-particle distances by applying the electric fieldwhen the particles having electric charges are dispersed in a solventhaving electrical polarization characteristic in accordance with oneembodiment of the present invention;

FIGS. 47 and 48 are graphs illustrating the wavelength of lightreflected from the particles as a result of performing an experimentimplementing the first mode by applying an electric field when theparticles having electric charges are dispersed in various solventshaving different polarity indices in accordance with one embodiment ofthe present invention;

FIGS. 49 and 50 are graphs and photographs illustrating light reflectedfrom the particles as a result of performing an experiment implementingthe first mode by applying an electric field when the particles havingelectric charges and the electrical polarization characteristic aredispersed in a solvent;

FIG. 51 is a view illustrating results performing experiments fordependency (that is, the viewing angle of the display device) of anobservation angle of the display device in accordance with oneembodiment of the present invention;

FIG. 52 is a view illustrating experimental results of the displaydevice capable of selectively switching any one of the first and secondmodes in accordance with one embodiment of the present invention;

FIGS. 53 and 54 are views illustrating experimental results of thedisplay device capable of selectively switching any one of the first andthird modes in accordance with one embodiment of the present invention;

FIGS. 55A, 55B, 55C and 56 are views illustrating experimental resultsof the display device capable of selectively switching any one of thesecond and third modes in accordance with one embodiment of the presentinvention;

FIG. 57 is a view illustrating one embodiment of the mode switchingconfiguration in the second mode;

FIG. 58 is a view illustrating one embodiment of the mode switchingconfiguration in the third mode; and

FIG. 59 is a graph illustrating mode implementation and a relation amonga wavelength, application voltage and reflectance for implementing themode switching.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following detailed description, reference is made to theaccompanying drawings that show, by way of illustration, specificembodiments in which the invention may be practiced. These embodimentsare described in sufficient detail to enable those skilled in the art topractice the invention. It is to be understood that the variousembodiments of the invention, although different from one another, arenot necessarily mutually exclusive. For example, a particular feature,structure and characteristic described herein in connection with oneembodiment may be implemented within other embodiments without departingfrom the spirit and scope of the present invention. Also, it is to beunderstood that the locations or arrangements of individual elements inone embodiment may be changed without separating the spirit and scope ofthe present invention. When “in accordance with one embodiment” or “oneembodiment” generally used in the specification appears, this is not tobe construed that a shape, a structure, a characteristic, a method, aconfiguration, etc., described in the specific one embodiment are notnecessarily applied to all the embodiments. In addition, it is not to beconstrued that the shape, structure, method, configuration, etc.,described in the specific embodiment are applied only to the specificembodiment. In addition, the shape, structure, feature parts,characteristics, configuration, etc., used in the specific embodimentsmay be combined with other embodiments.

In addition, a singular form of a noun used in the specification doesnot exclude a presence of a plural form. Also, used herein, the word“comprising”, “having” and “including” and inflected words thereof willbe understood to imply the inclusion of stated constituents, steps,operations and/or elements but not the exclusion of any otherconstituents, steps, operations and/or elements. Further, a sequence ofsteps of a process used in the specification is not limited to onedescribed in the specification but another sequence may also be present.Ordinal numerals used in the specification, “first”, “second”, “third”,etc., is to differentiate components, modes or steps from one anotherand does not have the meaning of any sequence. In addition, the specificmode may be referred to as a first mode, a second mode or a third mode.For example, in the specification, the first mode indicates a photoniccrystal reflection mode, but in claims, the first mode may be othermodes other than the photonic crystal reflection mode. In addition, inthe specification, the second mode may indicate the unique colorreflection mode, but in claims, may be other mode other than the uniquecolor reflection mode. This is also applied to the third mode. That is,in order to systemically describe the present invention, although thespecification describes each mode using the first mode as the photoniccrystal reflection mode, the second mode as the unique color reflectionmode and the third mode as the transmittance tuning mode, the presentinvention is not limited to the description manner.

The following detailed description is, therefore, not to be taken in alimiting sense, and the scope of the invention is defined only by theappended claims that should be appropriately interpreted along with thefull range of equivalents to which the claims are entitled. In thedrawings, like reference numerals identify identical or like elements orfunctions through the several views.

Hereinafter, the configuration of the present invention will bedescribed in detail with reference to the accompanying drawings so thatthose skilled in the art can easily carry out the present invention.

Configuration of Display Device

A display device according to an embodiment of the present invention canbe selectively implemented so as to switch at least two of a first mode(photonic crystal reflection mode) for displaying a color of lightreflected from photonic crystals composed of particles, a second mode(unique color reflection mode) for displaying a unique color such asparticles, solvents, electrodes, etc., or a color of a solution due to ascattering of particles and a third mode (transmittance tuning mode) fordisplaying (that is, tuning the transmittance of light) the color oflight with the tuned transmittance to each other within a display regionof the display device or the same unit pixel of a display unit byapplying an electric field through an electrode when particles aredispersed in a solvent and controlling at least one of the intensity,direction, application time, application frequency and applicationregion of an electric field to control at least one of an interval, alocation and an arrangement of particles. As can be appreciated from thefollowing description, the unit pixel means a minimum display unit thatcan be independently controlled. That is, in the existing displaymethod, a red cell, a green and a blue cell may form the single unitpixel. For example, three cells form the single unit pixel in the methodimplementing colors by a mixing of R, G and B colors. The presenttechnology can implement continuous colors by independently controllingthe single unit cell or the unit pixel, and therefore, unlike theexisting method, it should be noted that the unit pixel in thespecification means a minimum display unit, a display region or adisplay unit, which can be independently controlled.

Composition of Particles and Solvents

FIGS. 1 and 2 are views illustrating the configuration of particlescontained in a display device in accordance with one embodiment of thepresent invention.

First, referring to FIG. 1, particles 110 in accordance with oneembodiment of the present invention may be present in a solution stateby being dispersed in a solvent 120. In accordance with one embodimentof the present invention, the particles 110 may have positive charges ornegative charges. Therefore, when electric field is applied to theparticles 110, the particles 110 may be moved (that is, electrophoresis)due to electrical attraction generated by electric charges and electricfield of the particles 110. In addition, when particles 110 has electriccharges of the same sign, particles 110 may be arranged with apredetermined interval without contacting each other due to electricalrepulsion (coulomb repulsion) therebetween by the electric charges ofthe same sign. In addition, in accordance with one embodiment of thepresent invention, the particles 110 are coated in a polymer chain form,etc., which may be resulted in a steric effect due to a chaotic motion,etc., of an inter-particle polymer chain. Therefore, particles 110 maybe arranged with a predetermined interval without contacting each otherdue to the inter-particle steric effect.

Referring to FIG. 2, the particles 110 in accordance with one embodimentof the present invention may have a core-shell 112 configuration madefrom different types of materials as shown in FIG. 2(a), a multi-core114 configuration made from different kinds of materials as shown inFIG. 2(b), or a cluster structure 116 made from a plurality ofnano-particles as shown in FIG. 2(c), wherein a charge layer 118 havingelectric charges or a layer 118 indicating the steric effect describedabove may be configured to have a structure enclosing the particles. Theparticles in accordance with one embodiment of the present invention isnot limited to the structure and therefore, one embodiment of thepresent invention may use various particles and forms such as astructure in which a heterogeneous material is permeated or immersedinto core particles, a raspberry structure, etc., and may also use acavity structure such as a reverse photonic crystal structure.

More specifically, the particles 110 in accordance with one embodimentof the present invention may be made of elements, such as silicon (Si),titanium (Ti), barium (Ba), strontium (Sr), iron (Fe), nickel (Ni),cobalt (Co), lead (Pb), aluminum (Al), copper (Cu), silver (Ag), gold(Au), tungsten (W), molybdenum (Mo), zinc (Zn), zirconium (Zr) or acompound such as oxide, nitride, etc., including the same. Also, theparticles 110 in accordance with one embodiment of the present inventionmay be made of organic polymers including at least one monomer ofstyrene, pyridine, pyrrole, aniline, pyrrolidone, acrylate, urethane,thiophene, carbazole, fluorene, vinylalcohol, ethylene glycol and ethoxyacrylate or polymer materials such as PS (polystyrene), PE(polyethylene), PP (polypropylene), PVC (polyvinyl chloride) and PET(polyethylene terephthalate).

In addition, the particles 110 in accordance with one embodiment of thepresent invention may be made by coating particles or a cluster havingno electric charge with a material having electric charges. Examples ofthese particles may include particles whose surfaces are processed (orcoated) with an organic compound having a hydrocarbon group; particleswhose surfaces are processed (or coated) with an organic compound havinga carboxylic acid group, an ester group and an acyl group; particleswhose surfaces are processed (or coated) with a complex compoundcontaining halogen (F, Cl, Br, I, etc.) elements; particles whosesurfaces are processed (coated) with a coordination compound containingamine, thiol and phosphine; and particles having electric chargesgenerated by forming radicals on the surfaces. As described above, thesurface of the particles 110 is coated with materials such as silica,polymer, monomer, etc., such that the particles 110 may have highdispersibility and stability within the solvent 120.

Meanwhile, a diameter of the particles 110 may range from several nm toseveral hundred μm, but the diameter of the particles is not necessarilylimited thereto. When the particles are arranged at a predetermineddistance by the external electric field, the size of the particles isset to be able to include the photonic crystal wavelength band of thevisible spectrum by the Bragg's law in connection with the refractiveindex of the particles and the refractive index of the solvent.

Meanwhile, in accordance with one embodiment of the present invention,the particles 110 may be configured to have a unique color, therebyreflecting light having a specific wavelength. More specifically, theparticles 110 in accordance with one embodiment of the present inventionmay have a specific color through an oxidation state control or acoating such an inorganic pigment, pigment, etc. For example, as theinorganic pigments coated on the particles 110 in accordance with oneembodiment of the present invention, Zn, Pb, Ti, Cd, Fe, As, Co, Mg, Al,etc., including chromophore may be used as a form of oxide, emulsion andlactate and as the dyes coated on the particles 110 in accordance withone embodiment of the present invention, a fluorescent dye, an acid dye,a basic dye, a mordant dye, a sulfur dye, a vat dye, a disperse dye, areactive dye, etc., may be used. In addition, in accordance with oneembodiment of the present invention, the particles 110 may be made of amaterial having a specific structural color so as to display thespecific colors. For example, the particles such as oxide silicon(SiO_(x)), oxide titanium (TiO_(x)), etc., are configured to beuniformly arranged in media having different refractive indices at apredetermined distance so as to reflect light having a specificwavelength.

Further, in accordance with one embodiment of the present invention, thesolvent 120 may also be configured to reflect light having a specificwavelength, that is, a unique color. More specifically, the solvent 120in accordance with one embodiment of the present invention may includematerials having inorganic pigments, dyes or materials having astructural color by the photonic crystal.

In addition, in accordance with one embodiment of the present invention,the particles or the solvent include at least one of fluorescentmaterials, phosphor materials, luminous materials, etc., therebymaximizing the effects of one embodiment of the present invention.

In accordance with one embodiment of the present invention, in order tosecure colloidal stability of the particles 110 by uniformly dispersingthe particles 110 in the solvent 120, surfactants such as dispersants,etc., may be added to the solvent 120 so that the particles 110 arestably dispersed within the solvent 120 or a difference in a specificgravity between the particles 110 and the solvent 120 may be apredetermined value or less. Further, the viscosity of the solvent 120may be a predetermined value or more, or a value of electrokineticpotential (that is, zeta potential) of a collide solution composed ofthe particles 110 and the solvent 120 may be a predetermined value ormore.

In addition, in accordance with one embodiment of the present invention,in order to increase the intensity of reflected light in a visible lightregion generated through a predetermined arrangement of the particles110 within the solvent 120 when an electric field is applied, adifference in refractive indices between the solvent 120 and theparticles 110 may be a predetermined value or more and the size of theparticles 110 may be set to be the size of the particles of the photoniccrystal wavelength band of the visible light region in connection withthe refractive index of the particles and the refractive index of thesolvent by the Bragg's Law.

For example, an absolute value of the electrokinetic potential of thecollide solution may be 10 mV or more, the difference in specificgravity between the particles 110 and the solvent 120 may be 5 or less,and the difference in the refractive index between the particles 110 andthe solvent 120 may be 0.3 or more, and the size of the particles may bea range from 100 nm to 500 nm, but are not limited thereto.

Inter-Particle Attraction: Electrical Polarization Characteristic

In addition, in accordance with one embodiment of the present invention,the solution including the solvent, in which the particles included inthe display device are dispersed, may have variable electricalpolarization characteristic, which is a characteristic that an amount ofelectrical polarization varies when the electric field is applied. Inthe electrical polarization characteristic of the solution, at least oneof the particles or the solvent configuring the solution may indicatethe electrical polarization characteristic or the electricalpolarization characteristic may occur due to the interaction between theparticles and the solvent within the solution. Further, the solution(composed of the particles and solvent) indicating the electricalpolarization characteristic may include a material which is electricallypolarized with any one of electronic polarization, ionic polarization,interfacial polarization or rotational polarization due to asymmetricalcharge distribution of atoms or molecules as an external electric fieldis applied.

Therefore, at least one of the particles or the solvent or the solutioncomposed thereof in accordance with one embodiment of the presentinvention may cause the electrical polarization when the electric fieldis applied and the induced electrical polarization may be changed as theintensity or direction of applied electric field is changed. Thecharacteristics of changing the electrical polarization according to thechange in the electric field may be the variable electrical polarizationcharacteristic. In one embodiment of the present invention, it is morepreferable to increase the electrical polarization induced when theelectric field is applied. The reason is that the inter-particledistances may be more uniformly arranged by more greatly applying theinter-particle interaction force by the electrical polarization of atleast one of the particles, the solvent and the solution.

FIG. 3 is a view illustrating the configuration of polarization ofparticles or solvent upon application of an electric field in accordancewith one embodiment of the present invention.

Referring to FIGS. 3(a) and 3(b), when the external electric field isnot applied, the particles or the solvent maintains an electricalequilibrium state, such that the electrical polarization characteristicis not shown, but when the external electric field is applied, thepolarization is induced as the electric charges within the particles orthe solvent moves in a predetermined direction, such that the particlesor the solvent may be polarized. FIGS. 3(c) and 3(d) show the case inwhich unit polarization is generated by electrically asymmetriccomponents composing the particles or the solvent. If no externalelectric field is applied, the unit polarization is arrangedchaotically, such that the whole electrical polarization is not shown orshows a small value. Whereas, if the external electric field is applied,the particles or the solvent having the unit polarization may bere-arranged in a predetermined direction along the direction of theexternal electric field and, thus, may show a relatively largepolarization value as compared with the case of FIG. 3(b) where theelectric field is applied when the unit polarization is not generallypresent. In accordance with one embodiment of the present invention, theunit polarization shown in FIGS. 3(c) and 3(d) may occur in theasymmetrical arrangement of electrons or ions or the asymmetricalstructure of molecules. When no external electric field is applied, avery small remnant polarization value may be shown as well due to thisunit polarization.

FIG. 4 is a view illustrating unit polarization characteristic exhibitedby the asymmetrical arrangement of molecule in accordance with oneembodiment of the present invention. More specifically, FIG. 4illustrates the case of water molecules (H2O). In addition to the watermolecules, trichloroethylene, carbon tetrachloride, di-iso-propyl ether,toluene, methyl-t-bytyl ether, xylene, benzene, diethyl ether,dichloromethane, 1,2-dichloroethane, butyl acetate, iso-propanol,n-butanol, tetrahydrofuran, n-propanol, chloroform, ethyl acetate,2-butanone, dioxane, acetone, methanol, ethanol, acetonitrile, aceticacid, dimethylformamide, dimethyl sulfoxide, propylene carbonate,N,N-Dimethylformamide, Dimethyl Acetamide, N-Methylpyrrolodone, etc.,may be employed as the material constituting the particles or solventbecause they represent the unit polarization characteristic due to theasymmetry of a molecular structure. For reference, the polarity indexused to compare the polarization characteristics of materials is anindex that shows the relative degree of polarization of a given materialwith respect to the polarization characteristic of water (H₂O). Inaccordance with one embodiment of the present invention, the solvent mayinclude materials whose polarity index is 1 or more.

Moreover, the particles or solvent in accordance with one embodiment ofthe present invention may include a ferroelectric material, which showsa large increase in polarization by further causing the electricalpolarization of ions or atoms upon application of an external electricfield, a remnant polarization even without the application of anexternal electric field, and remnant hysteresis along the applicationdirection of the electric field. The particles or solvent may include asuperparaelectric material, which shows a large increase of polarizationby further causing the polarization of ions or atoms upon application ofan external electric field but shows no remnant polarization and noremnant hysteresis when no external electric field is applied. Referringto FIG. 5, it can be seen that there are hysteresis curves which areobtained according to the external electric fields of a paraelectricmaterial 510, the ferroelectric material 520 and the superparaelectricmaterial 530.

Further, the particles or solvent in accordance with one embodiment ofthe present invention may include a material having a perovskitestructure. Examples of materials having a perovskite structure, such asABO₃, may include materials such as PbZrO₃, PbTiO₃, Pb(Zr,Ti)O₃, SrTiO₃,BaTiO₃, (Ba, Sr)TiO₃, CaTiO₃, LiNbO₃, etc.

FIG. 6 is a view illustrating a material having a perovskite structurethat may be included in the particles or solvent in accordance with oneembodiment of the present invention. Referring to FIG. 6, the locationof Zr (or Ti) in PbZrO3 (or PbTiO₃)(i.e., B in an ABO₃ structure) mayvary with the direction of the external electric field applied to PbZrO₃(or PbTiO₃), and thus, the overall polarity of PbZrO₃ (or PbTiO₃) may bechanged. Therefore, the asymmetrical electron distribution is formed bya movement of atoms or ions so that unit polarization may be formed.When the unit polarization is present, a larger variable electricalpolarization value may be induced when the external electric field isapplied, as compared with the case in which only the electronpolarization is present.

In addition, in accordance with one embodiment of the present invention,the reflected light tuning and transmittance tuning effect of oneembodiment of the present invention may be maximized as theinter-particle arrangement is better. Therefore, the effect of oneembodiment of the present invention may be maximized by using a fluidshowing an electro-rheology (ER) characteristic by dispersing the fineparticles in an insulator fluid or a fluid showing a giantelectro-rheology (GER) such as ferroelectric particles coated with aninsulator.

In addition, in describing an aspect of the electrical polarization, asa first example, at least one of each molecule and each particle of thesolvent does not any electrical polarization when the electric field isnot applied, but at least one of each molecule and each particle of thesolvent is electrically polarized when the electric field is applied.Thereby, at least one of a total of electric polarization of particlesand a total electric polarization of the solvent may be increased. In asecond example, when the electric field is not applied, at least one ofeach molecule and each particle of the solvent is electricallypolarized, but at least one of the total of electrical polarization ofthe solvent and the total electrical polarization of particles becomeszero and when the electric field is applied, at least one of the totalof electric polarization of particles and the total of electricpolarization of the solvent may be increased. In a third example, whenthe electric field is not applied, at least one of each molecule andeach particle of the solvent is electrically polarized and at least oneof the total of electrical polarization of the solvent and the totalelectrical polarization of particles has a first value, which is notzero, and when the electric field is applied, at least one of the totalof electric polarization of particles and the total of electricpolarization of the solvent may have a second value larger than thefirst value.

Inter-Particle Repulsion: Coulomb Effect or Steric Effect

In accordance with one embodiment of the present invention, the surfacesof the particles included in the display device are charged withelectric charges of the same sign such that coulomb repulsion is formedon the particles or the surfaces of the particles are provided with asteric structure, etc., such as a polymer chain structure, a functionalgroup, a surfactant, etc., thereby forming the steric hindrancerepulsion.

In addition, in accordance with one embodiment of the present invention,in order to maximize the inter-particle repulsion, the coulomb repulsionand the steric hindrance repulsion may also be simultaneously induced bycharging the particles with electric charges of the same sign andcoating the particles in the steric structure form.

Further, in accordance with one embodiment of the present invention, theparticles include electrically polarized materials. As a result, anelectrophorectic effect may be minimized due to the weakly chargedcharges although the inter-particle steric hindrance repulsion ispresent through the particle surface treatment, such that the particlesor the solution has the electrical polarization changed according to theexternal electric field, thereby effectively generating theinter-particle short range attraction and the inter-particle short rangesteric hindrance repulsion is effectively generated by the stericstructure formed through the particle surface treatment. Further, itbecomes possible to minimize a phenomenon that the particles charged bythe long range electrophorectic force due to the external electric fieldare collected to the electrode. That is, the electric charges on thesurface of the particles are not treated, such that the electrophorecticphenomenon of collecting the particles to any one electrode by theexternal electric field may be minimized. In order to give the sterichindrance repulsion, an organic ligand may be treated on the surface ofthe particles. Further, in accordance with one embodiment of the presentinvention, in order to prevent the phenomenon that the particles chargedby the electrophoresis are collected to the electrode when the chargedparticles are used, a combination of AC voltage rather than DC voltagemay also be used.

However, a composition of the particles and solvent in accordance withone embodiment of the present invention is not limited to the above listand therefore, but may be appropriately changed within the range capableof achieving the objects of the present invention, that is, the range inwhich the inter-particle distances may be controlled by the electricfield.

For example, in order to maximize the effects of the present invention,opaque is increased by increasing the difference in the refractiveindices between the particles and the solution in which the particlesare dispersed to maximize the scattered reflection (scattering) whenvoltage is not applied and the reflectance of the structural color maybe increased when the structural color is exhibited by applying voltage.Generally, since the refractive index of the fluid has no largedifference according to a type, a method for maximizing the refractiveindex of the particles is effective and the particles may bemanufactured by a raspberry structure or a core/shell structure, etc. inwhich at least two of different materials are combined, therebymaximizing both of the above-mentioned refractive index effect and therepulsion effect.

Operating Principle and Configuration of First Mode (Photonic CrystalReflection Mode)

The display device in accordance with one embodiment of the presentinvention applies the electric field through the electrode whenparticles are dispersed in the solvent and controls the inter-particledistances by controlling at least one of the intensity, direction,application frequency and application time of the electric field,thereby performing the first mode which variably displays the color oflight reflected from the particle structure (that is, the photoniccrystals formed by maintaining particles at the predetermined distance).Hereinafter, the operating principle and configuration of the first modeof the display device in accordance with one embodiment of the presentinvention will be described in detail. In the specification and claims,the first mode may often be referred to as a photonic crystal reflectionmode. Meanwhile, in the specification, the transmitted light may also bepresent in the reflection mode (the photonic crystal reflection mode andthe unique color reflection mode (corresponding to a second mode to bedescribed later)). However, in one embodiment of the present invention,since the reflected light predominantly generated in the reflection modeis used, the use of the transmitted light may be disregarded. Inaddition, since one primarily predominantly generated in thetransmittance tuning mode that is the third mode to be described belowis the transmitted light, the use of the primarily reflected light isalso disregarded. That is, in the specification, it is apparent that thelight predominantly generated in the corresponding mode is used.Further, as described above, in the claims, the first mode may be a modedifferent from the photonic crystal reflection mode. Thus, such a modeis for only the systematic description and therefore, the presentinvention is not limited thereto.

First, in accordance with a first embodiment of the first mode of thedisplay device of the present invention, when particles having electriccharges of the same sign or polarity are dispersed in a solvent havingelectrical polarization characteristic, if an electric field is appliedto the dispersion including the particles and solvent containing thedispersed particles, electrical force proportional to the intensity ofthe electric field and the charge amount of the particles acts on theparticles due to the electric charges of the particles. Therefore,particles move in a predetermined direction by electrophoresis, thusnarrowing the inter-particle distances. Meanwhile, in contrast,electrical repulsion generated between the particles having the electriccharges of the same sign or polarity increases as the inter-particledistances become smaller resulting in a predetermined equilibrium statewhile preventing the inter-particle distances from continuing todecrease. Therefore, particles may be regularly arranged at apredetermined distance. In addition, the solvent around the particlescharged with electric charges is electrically polarized due to theelectrical polarization characteristic and are affected to each otherand the electric polarization of the solvent are arranged in theexternal electric field direction. Therefore, the particles charged withthe electric charges locally interacted with the electrical polarizationof the solvent may also be arranged in the direction of the externalelectric field. That is, the unit polarized solvent is arranged in apredetermined direction by the externally applied electric field and thecharges of the peripheral particles. Therefore, the locally formedpolarization region is formed based on the particles, such that theparticles may be more regularly and stably arranged while maintainingthe predetermined distance. In accordance with the first embodiment ofthe present invention, particles can be regularly arranged at distanceswhere electrical attraction (electrophorectic force) induced by anexternal electric field, electrical force (coulomb repulsion) betweenthe particles having electric charges of the same polarity, electricalattraction (coulomb attraction) induced by polarization, etc., are inequilibrium. According to the above principle, the inter-particledistances can be controlled at predetermined distance, and the particlesarranged at predetermined distances can function as photonic crystals.Since the wavelength of light reflected from the regularly spacedparticles is determined by the inter-particle distances, the wavelengthof the light reflected from the particles can be arbitrarily controlledby controlling the inter-particle distances through the control of theexternal electric field. Here, a pattern of the wavelength of reflectedlight may be diversely represented by the factors, such as the intensityand direction of the applied electric field, the size and mass of theparticles, the refractive indices of the particles and solvent, thecharge amount of the particles, the electrical polarizationcharacteristic of the solvent or the particles, the concentration of theparticles dispersed in the solvent, etc.

FIG. 7 is a view conceptually illustrating a configuration ofcontrolling inter-particle distances in accordance with a firstembodiment of a first mode of a display device of the present invention.Referring to FIG. 7, if no external electric field is applied, unitpolarized solvent 710 near particles 720 having electric charges can beintensively arranged in the direction of the particles by interactionwith the electric charges of the particles, and the unit polarizedsolvent 710 can be arranged more chaotically or randomly as its distancefrom the charged particles increases (See FIG. 7(a)). In addition,referring to FIG. 7, if an external electric field is applied, the unitpolarized solvent 710 located in a region not affected by the electriccharges of the particles 720 (i.e., a region far away from the particles720) is re-arranged in the direction of the electric field and thecharged particles 720 may be re-arranged by the affect of the rearrangedsolvent. That is, the unit polarized solvent 710 located in a regionstrongly affected by electrical attraction induced by the particlescharged with the electric charges (i.e., a region closed to theparticles 720) can be arranged in a direction in which an anode or acathode of the unit polarization is toward the particles 720 byinteraction the electrical attraction induced by the electric charges ofthe particles 720. As such, the region where the unit polarizationsolvent 710 in the surrounding region of the particles 720 is arrangedtoward the particles 720, i.e., a polarization region 730, acts like onelarge, electrically polarized particles, and thus, can interact withother large polarization regions, thereby enabling the particles 720having electric charges to be regularly arranged while maintaining apredetermined interval or space therebetween (See FIG. 7(b)). AlthoughFIG. 7 shows a solvent having a remnant polarization, a solvent havingthe electrical polarization characteristic induced by the application ofthe electric field even when no remnant electrode is may be alsoapplied.

Next, in accordance with a first embodiment of the first mode of thedisplay device of the present invention, when particles having electriccharges of the same sign or polarity are dispersed in a solvent havingelectrical polarization characteristic, if an electric field is appliedto the dispersion including the particles and solvent containing thedispersed particles, electrical force proportional to the intensity ofthe electric field and the charge amount of the particles acts on theparticles due to the electric charges of the particles. Therefore,particles move in a predetermined direction by electrophoresis, thusnarrowing the inter-particle distances. Meanwhile, in contrast,electrical repulsion generated between the particles having the electriccharges of the same sign or polarity increases as the inter-particledistances become smaller, resulting in a predetermined equilibrium statewhile preventing the inter-particle distances from continuing todecrease. Therefore, particles may be regularly arranged at apredetermined distance. In addition, the particles showing theelectrical polarization characteristic are polarized by the electricfield and are thus polarized in the direction of the electrical field,and thus, the electrical attraction is locally generated among theplurality of polarized particles, such that the particles may be moreregularly and stably arranged while maintaining the predetermineddistance. That is, in accordance with the aforementioned embodiments ofthe display device of the present invention, particles can be regularlyarranged at distances where the electrical attraction (electrophorecticforce) induced by an external electric field, electrical repulsion(coulomb repulsion) between the particles having electric charges of thesame sign, the electrical attraction (coulomb attraction) induced bypolarization are in equilibrium. According to the above principle, theinter-particle distances can be controlled at a predetermined distance,and the particles arranged at predetermined distances can function asphotonic crystals. Since the wavelength of light reflected from theregularly spaced particles is determined by the inter-particledistances, the wavelength of the light reflected from the particles canbe arbitrarily controlled by controlling the wavelength of lightreflected from particles according to the control of the inter-particledistances. Here, a pattern of the wavelength of reflected light may bediversely represented by the factors, such as the intensity anddirection of the applied electric field, the size and mass of theparticles, the refractive indices of the particles and solvent, thecharge amount of the particles, the electrical polarizationcharacteristic of the particles and solvent, the concentration of theparticles dispersed in the solvent, etc.

FIG. 8 is a view conceptually illustrating a configuration ofcontrolling inter-particle distances in accordance with a secondembodiment of the first mode of the display device of the presentinvention. Referring to FIG. 8, if no external electric field isapplied, particles 810 are not polarized (see FIG. 8(a)). If an externalelectric field is applied, the particles 810 can be electricallypolarized due to the electrical polarization characteristic of thematerial in the particles 810. Accordingly, the particles 810 can beregularly arranged while maintaining a predetermined interval or spacetherebetween (see FIG. 8(b)).

In the first and second embodiments of the present invention, thegreater the electrical polarization value of the solvent or particles,the higher the degree of interaction between the polarization regions730 or between the polarized particles 810, thereby enabling theparticles to be more regularly arranged. FIG. 8 shows the particleshaving no remnant polarization. However, it may be also applied to theparticles having the electrical polarization characteristic changed bythe application of the electric field even when the remnant polarizationis present.

Meanwhile, FIGS. 9 and 10 conceptually illustrate the configuration ofthe display device in accordance with one embodiments of the first modeof the display device in accordance with one embodiment of the presentinvention. The embodiments of the first mode of the display device ofthe present invention were described in detail with reference to FIGS. 7and 8 and therefore, the additional description of FIGS. 9 and 10 willbe described.

Although the embodiment of the first mode as described above describesthe case in which the particles or the solvent has the electricalpolarization characteristic, it is to be noted that the particles or thesolvent in accordance with one embodiment of the present invention doesnot necessarily have the electrical polarization characteristic. Thatis, if the particles have electric charges even when the particles orthe solvent does not have the electrical polarization characteristic,particles can be regularly arranged at distances where the electricalattraction due to the external electric field and the electricalrepulsion between particles having electric charges of the same sign arein an equilibrium state. As such, the plurality of regularly arrangedparticles may form the photonic crystals that reflect light having anywavelength.

In the first mode of the present invention, although the inter-particledistances may be constantly maintained by the equilibrium of attractionand repulsion acting on the particles according to the external electricfield as described above, the arrangement of the particles in accordancewith the present invention may be three-dimensionally shown in shortrange ordering rather than long range ordering since the attraction andthe repulsion may effectively act between particles in the short rangebut the interaction force cannot effectively act between the particlesabove the predetermined distance. In addition, the reflected light thatis reflected due to the set of the short range ordering having finelydifferent orientation may show the reflected light characteristics withgreatly improved viewing angle dependency as compared with the photoniccrystal light reflected by the existing typical photonic crystalarrangement. In addition, although the embodiment of the first mode asdescribed above describes the case in which the particles have electriccharges, it is to be noted that the particles in accordance with thepresent invention does not necessarily have electric charges. That is,if the particles have the electric polarization characteristic and havethe steric structure that generates the steric hindrance repulsion evenwhen the particles do not have the electric charges, particles may beregularly arranged at distances where the electrical attraction betweenthe adjacent particles due to the electrical polarization induced by anexternal electric field and the repulsion due to the steric effect arein an equilibrium state. As such, the plurality of regularly arrangedparticles may form the photonic crystals that reflect light having anywavelength. In other words, if particles exhibit the mutual stericeffect, the electrostatic attraction acting between the particles by thevariable electrical polarization characteristic and the steric hindrancerepulsion acting between the particles acts on each other according tothe application of the electric field, such that the inter-particledistances reach a specific range. Further, the light having the specificwavelength is reflected from particles as the inter-particle distancesreach the specific range, thereby implementing the specific hue.

FIG. 11 is a view exemplarily illustrating the configuration of thefirst mode in accordance with one embodiment of the present invention.Referring to FIG. 11, as the intensity of applied electric field isincreased, the inter-particle distances of the particles 1112 becomesnarrow, and thus, the wavelength of light reflected from the photoniccrystals composed of the particles 1112 may become short. Therefore, thewavelength range of light reflected from the particles 1112 may becontinuously controlled by controlling the intensity and direction ofthe electric field. Meanwhile, FIG. 11 shows a case in which a lowerelectrode is divided into a large electrode and a small electrode, butthe present invention is not limited thereto and therefore, the lowerelectrode may be integrally formed. That is, the electrode may bedivided or integrated according to each embodiment. It can be understoodbased on the following description that the electrode may need to beintegrated and the electrode may need to be divided in some modeswitching embodiments. For reference, in case of one specific modeswitching, since the embodiment of the present invention switches modesin the same unit pixel, it is apparent that the structure of thecorresponding electrode is not changed.

Further, the voltage applied to implement the first mode may be DCvoltage or AC voltage or AC voltage including DC components. Both of theelectrical polarization characteristic or the variable electricalpolarization characteristic as described above may be generated when theAC voltage or DC voltage is applied. In particular, when the DC voltageis applied to the charged particles, the particles charged by theelectrophoresis moves to the electrode applied with opposite electriccharges, and thus, the electric charges are concentrated to theelectrode. As a result, the particles are subjected to the graduallychanging electrophorectic force since the screen phenomenon induced bythe concentrated electric charges affects other particles. Consequently,the particles may be maintained at a gradually changing distance in thedirection of the electric field and have short range regularity ratherthan long range regularity, thereby configuring the display unit havingthe excellent viewing angle. The viewing angle characteristics will bedescribed below.

In addition, the drawings of the present invention show that theparticles are chaotically dispersed to show the solution color whenvoltage is not applied. However, if the concentration of the particlesis higher than the predetermined value and the inter-particleinteraction force is sufficient even when the voltage is not applied,then the specific distance may be maintained by the inter-particleinteraction without applying the voltage.

Operating Principle and Configuration of Second Mode (Unique ColorReflection Mode)

In accordance with a display device of a second mode of the presentinvention, a location of particles can be controlled by applying anelectric field through an electrode when the particles are dispersed ina solvent and controlling at least one of the intensity, direction,application time, application frequency and application region of theelectric field, such that a color of a solution or a color of anelectrode is variably displayed due to a unique color or a holding colorof the particles or the solvent or the light scattering of theparticles. However, in the specification and claims, when the electrodeis a transparent electrode, the electrode color indicates a color thatis shown by a material under the transparent electrode and second modemay be referred to as a unique color reflection mode or a holding colorreflective mode. In this case, the unique color may mean a colorreflected when a material of the particles, the solvent or the electrodeirradiates white light.

The second mode of the display device in accordance with one embodimentof the present invention may be implemented by moving the particleshaving electric charges by using electrophoresis (EP) or moving theparticles having predetermined dielectric constant different from thesolvent by using dielectrophoresis (DEP). The electrophoresis anddielectrophoresis phenomenon may be more efficiently generated when DCvoltage is applied to the dispersed solvent.

First, the embodiment implementing the second mode of the display devicein accordance with the present invention using the electrophoresis willbe described below.

First, in accordance with the second mode of the display device inaccordance with the present invention, when particles having electriccharges of the same sign or polarity are dispersed in a solvent, if anelectric field is applied to the dispersion including the particles andsolvent containing the dispersed particles, electrical attractionproportional to the intensity of the electric field and the chargeamount of the particles acts on the particles due to the electriccharges of the particles. Therefore, particles move in a predetermineddirection by electrophoresis. In this case, when voltage is locallyapplied only to a portion of the electrode or voltage of a predeterminedvoltage or more is applied thereto, particles do not form the photoniccrystals as in the first mode and moves toward the local area of theelectrode applying the electric field.

FIG. 12 is a view exemplarily illustrating a configuration of a secondmode of the display device in accordance with one embodiment of thepresent invention.

Referring to FIG. 12, when the electric field is not applied, theparticles are irregularly dispersed in the solvent, and thus, the colorof the solution in which the unique colors of the particles and solventare mixed may be displayed (see FIG. 12(a)) (that is, referred to as thesolution color reflection mode in which the color of the color isindicated by the light scattering by the particles); the particles 1212move toward an observer, that is, an upper electrode 1230, and thus, theunique color of the particles 1212 may be displayed (see FIG. 12(b))(referred to as the particle color reflection mode); the particles 1212may move toward a first lower electrode 1240 (referred to as a largeelectrode) that is opposite to the observer and has a wide area, andthus, the unique color of the solvent 1220 may be displayed (see FIG.12(c)) (referred to as the solvent color reflection mode) instead ofdisplaying the unique color of the particles 1212; and the particles1212 moves toward a second lower electrode 1250 (referred to as localelectrode or small electrode) that is opposite to the observer and has anarrow area, and thus, the unique color of the first lower electrode1240 may be displayed when the first lower electrode 1240 having a widearea is exposed (see FIG. 12(d)) (referred to as the electrode colorreflection mode). When the first lower electrode 1240 is transparent,the color of the material under the lower electrode displayed throughthe transparent lower electrode is referred to as the electrode color.Meanwhile, FIG. 12 shows that the lower electrode is divided into thelarge electrode 1240 and the small electrode or a local electrode 1250,but in the solution color reflection mode, the particle color reflectionmode and the solvent color reflection mode corresponding to FIGS. 12(a),12(b) and 12(c), the lower electrode may be formed in the integratedstructure. In addition, in the drawing, the small electrode or the localelectrode 1250 are exaggeratedly shown for the convenience ofexplanation but is very small compared with the large electrode 1240next thereto. Therefore, when being viewed from the top, it looks likethat the large electrode covers all of the lower electrode. In addition,although the specification shows the configuration in which the lowerelectrode is divided into the large electrode and the small electrode,the configuration in which the upper electrode is divided into the largeelectrode and the small electrode may also be considered. For example,when the upper electrode is divided into the large electrode and thesmall electrode, the particle color reflection mode may be implementedby applying voltage to only the large electrode, or the electrode colorreflection mode may be implemented only by applying voltage to only thesmall electrode. In other words, the embodiment implementing the uniquecolor reflection mode of the present invention is not limited to FIG. 12and therefore, may be diversely changed.

Next, the embodiment implementing the second mode of the display devicein accordance with the present invention using the dielectrophoresiswill be described below.

The dielectrophoresis phenomenon is a phenomenon that the non-chargeddielectric particles disposed in the dielectric medium applied with thenon-uniform electric field has an induced dipole moment and moves to theregion in which a gradient of the electric field is large or small bythe force applied to the dielectric particles by the difference betweenthe dielectric constant of the dielectric particles and the dielectricconstant of the dielectric medium. Therefore, the dielectric particleshaving the dielectric constant larger than the dielectric constant ofthe dielectric medium moves to the region in which the gradient of theelectric field is large and the dielectric particles having thedielectric constant smaller than the dielectric constant of thedielectric medium moves to the region in which the gradient of theelectric field is small.

FIG. 13 is a view exemplarily illustrating the configuration of thesecond mode of the display device in accordance with one embodiment ofthe present invention.

Referring to FIG. 13, it may be assumed that the dielectric constant ofparticles 1312 is larger than that of a solvent 1314 and the lowerelectrode is configured by being divided into first lower electrodes1332 and 1335 and a second lower electrode 1334. Referring to FIG.13(a), when voltage is not applied to the electrode, and thus, anelectric field is not applied to the particles 1312 and the solvent1314, since the particles 1312 is irregularly dispersed within thesolvent 1314, the unique color of the solution may be displayed.Meanwhile, referring to FIG. 13(b), when voltage is applied to firstlower electrodes 1332 and 1335 and a second lower electrode 1334, andthus, the first lower electrodes 1332 and 1335 are an electrode of apositive (+) sign and the second lower electrode 1334 is an electrode ofa negative (−) electrode, the gradient of the electric field generatedin the space between the first lower electrodes 1332 and 1335 and thesecond lower electrode 1334 is remarkably higher than the gradient ofthe electric filed generated in another region within the display unit,the particles 1312 moves by the dielectrophoresis so as to beconcentrated in the space between the first lower electrodes 1332 and1335 and the second lower electrode 1334, such that the unique color ofthe first lower electrodes 1332 and 1335 or the second lower electrode1334 may be displayed.

Meanwhile, the first mode described above is operated by the principleof the photonic crystals that selectively reflect the light having thespecific wavelength in light incident on the display device, such thatit is not easy to implement complete white or black. Therefore, whenusing the combination of white or black particles, solvent or electrodein the second mode, white or black that is the unique color of theparticles, solvent or electrode may be completely implemented, and thus,the disadvantage of the first mode as described above may besupplemented. More specifically, when using the white particles and theblack electrode (in case the electrode material is black or the blackmaterial is located on the lower portion of the transparent lowerelectrode), white that is the particle color or black that is theelectrode color may be selectively implemented within the same displayregion or the same unit pixel or the pixel according to theaforementioned mode switching.

Operating Principle and Configuration of Third Mode (TransmittanceTuning Mode)

In accordance with the third mode of the display device of the presentinvention, the transmittance of light transmitting at least one of theparticles or the solvent may be tuned by applying an electric fieldthrough an electrode when particles are dispersed in a solvent andcontrolling at least one of the intensity, direction, application time,application frequency and application region of an electric field tocontrol at least one of an interval, a location and an arrangement ofparticles. The third mode of the display device in accordance with thepresent invention may be implemented by controlling the wavelength ofthe reflected light by the photonic crystals (photonic crystaltransmittance tuning mode), moving the particles using theelectrophoresis or the dielectrophoresis (particlephoresis transmittancetuning mode), or controlling the arrangement state of particles(particle alignment transmittance tuning mode). Hereinafter, theembodiment of tuning the transmittance of light using three drivingprinciples as described above will each be described. In the embodiment,the third mode may be referred to as the transmittance tuning mode.Further, in the transmittance tuning mode, although the reflected lightis present but the transmitted light is dominantly generated, such thatit is to be noted that the light capable of being sensed by the observeris the transmitted light.

FIG. 14 is a view exemplarily illustrating a configuration of a thirdmode of the display device in accordance with one embodiment of thepresent invention.

First, referring to FIG. 14(a), in controlling the wavelength of lightreflected from the particle structure (that is, the photonic crystalsformed by maintaining particles at the predetermined distance) byapplying the electric field through the electrode when particles aredispersed in the solvent and controlling at least one of the intensityand direction of the electric field to control the inter-particledistances, the color of the display device may become transparent in thevisible region by controlling the electric field so as to be maintainedthe wavelength range of light reflected from the particles in anultraviolet or infrared spectrum rather than in the visible spectrum bycontrolling the intensity of the electric field applied to the particlesto make the inter-particle distances narrower or wider than a thresholdvalue. That is, the transmittance of light may be tuned by making thelight, which is reflected from the photonic crystals composed ofparticles, transparent. For reference, in the present invention, thetransmittance of light mainly means the transmittance of light in thevisible light region. In the specification, such a method may bereferred to as the photonic crystal transmittance tuning mode. Thephotonic crystal transmittance tuning mode may be generated in both ofthe DC voltage and the AC voltage and may be more efficiently shown whenthe solution in which the particles are dispersed has the aforementionedvariable electrical polarization characteristic. In one embodiment, whenthe ferroelectric or superparaelectric particles having the excellentelectrical polarization characteristic are used, the arrangement of theparticles is more efficiently shown due to the interaction between theelectrically polarized particles, thereby obtaining strongertransmittance.

Next, referring to FIG. 14(b), the corresponding particles areconcentrated on the electrode having a relatively narrow area byapplying the electric field to the particles that move by theelectrophoresis or the dielectrophoresis, such that the light incidenton the display device is not reflected or scattered by the particles,thereby tuning the transmittance of light. Meanwhile, although not shownin the drawing, the transmittance may also be tuned by controlling thedensity in which the particles are concentrated on the lower localelectrode. For example, it may also be considered the configuration oftuning the transmittance of light transmitting the particles and/or thesolvent by disposing the local electrode at the central portion of thelower electrode, and then, controlling the density in which theparticles are concentrated on the local electrode. Such a mode may bereferred to as the particlephoresis transmittance tuning mode in thespecification. This mode may be more efficiently made when the DCvoltage is applied and the transmittance may also be tuned according tothe application time or frequency of the DC voltage.

Next, referring to FIG. 14(c), when the electric field is applied to theparticles and solvent when particles having the electrical polarizationcharacteristic are dispersed in the solvent, particles are polarized bythe electric field, and thus, may be polarized in the same directionalong the direction of the electric field. Since the electricalattraction is generated between particles polarized in the samedirection, particles dispersed in the solvent are attracted to eachother, and thus, may be regularly arranged in a direction parallel tothe direction of the electric field. Therefore, the transmittance oflight incident on the solvent and the particles can be tuned bycontrolling the arrangement state of particles regularly arranged in adirection parallel to the direction of the electric field by controllingthe intensity or direction of the electric field. Although the drawingshows the case in which the alignment of the particles is relativelystraight, and thus, has the excellent transmittance, it may also beconsidered the case that the alignment degree of the particles has theweaker linear shape, and thus, the transmittance becomes low. Therefore,the present mode may be referred to as the particle arrangement or thealignment transmittance tuning mode. This mode may also be implementedby the DC voltage, but it is preferred to be implemented by applying ACvoltage so as to prevent the phenomenon biased to the electrode by theelectrophoresis when the DC voltage is applied. More specifically, inthe case of FIG. 14(c) controlling the arrangement of the particleshaving the electric charges and using the DC electric field, when theintensity of electric field applied to the particles and solvent isexcessively large or the electric field is locally applied, the lighthaving the unique color of the particles may be reflected orconcentrated on one side of the electrode by moving the particles towardthe electrode due to the electric attraction by the electrophoresis asin the second mode, and thus, it may be preferred to uniformly apply theAC electric field to the solution rather than DC.

Inter-Mode Switching within Same Unit Pixel or Cell

Hereinafter, the mode switching configuration, which is selectivelyimplemented so that at least two of the first, second and third modes ofthe present invention may be switched to each other within the same unitpixel or cell, will be described with reference to specific drawings.

(1) Switching Between First Mode and Second Mode within Same Unit Pixelor Cell

FIG. 15 is a view exemplarily illustrating a configuration of a displaydevice capable of being selectively performed so as to switch the firstand second modes to each other within the same unit pixel or cell inaccordance with one embodiment of the present invention.

Referring to FIG. 15, a display device 1500 in accordance with oneembodiment of the present invention may include a display unit 1510 andan electrode. More specifically, the display unit 1510 may includeparticles 1512 that are dispersed in a solvent 1514 and the electrodemay include an upper electrode 1530, a lower electrode 1540 and a localelectrode 1550. In addition, the particles 1512 and the solvent 1514included in the display unit 1510 and the lower electrode 1540 coveringthe bottom of the display unit 1510 may each have a unique color.Although the display unit and the electrode are separately described inthe specification for description, it is apparent that the electrode maybe included in the display unit. That is, a person having ordinary skillin the art to which the present invention pertains can understand thatthere is no problem in carrying out the present invention even when thedisplay unit has a configuration including both of the display unit andthe electrode in the representation linguistic aspect. In addition,although a detailed configuration of applying the electric field to thedisplay unit or the electrode is not shown, this is a component wellknown to a person having ordinary skill in the art to which the presentinvention pertains. Therefore, the components are omitted herein so asnot to obscure the principle and purpose of the present invention.Importantly, a control unit for switching the modes to each other withinthe unit pixel or a machine readable storage medium includinginstructions corresponding to the function of the control unit will bedescribed in detail. In addition, a person having ordinary skill in theart to which the present invention pertains may understand that the unitpixel is a minimum display unit that can be independently controlled. Inaddition, in FIG. 15, the upper electrode is a transparent electrode.

In accordance with one embodiment of the present invention, the displaydevice may selectively perform any one of the first mode and the secondmode within the same unit pixel so as to be switched to each other. Morespecifically, the display device in accordance with one embodiment ofthe present invention can apply the electric field through the electrodewhen particles are dispersed in the solvent and control at least one ofthe intensity and direction of the electric field, and thus, may controlthe inter-particle distances to control the wavelength of lightreflected from the photonic crystals composed of particles (first mode)or control the location of particles to perform a function of displayingthe hues (that is, a hue of a solution due to light scattering ofparticles), particles and solvent of the solution or the unique color ofthe electrode (second mode). Hereinafter, the color of the solution maybe considered as including the color of the solution due to the lightscattering of the particles.

First, referring to FIG. 15(a), the display device 1500 in accordancewith one embodiment of the present invention controls the inter-particledistances of the particles 1512 by controlling the intensity ordirection of the DC electric field applied to the solution indicatingthe variable polarization characteristic through electrodes 1530 and1540, thereby controlling the wavelength of light (that is, color)reflected from the particles 1512 (first mode). As described in detailwith reference to the first mode, when the particles 1512 have the sameelectric charges, the particles 1512 may be regularly arranged atdistances where the electrical attraction due to the external electricfield, the electrical repulsion between the particles 1512 havingelectric charges of the same sign, and the polarization due to theexternal electric field are in an equilibrium state and the particles1512 arranged at the predetermined distance may act as the photoniccrystal. Meanwhile, when the particles 1512 have the steric hindrancecapable of causing the steric hindrance effect, the particles 1512 maybe regularly arranged at distances where the repulsion between theparticles due to the steric effect and the electrical attraction due tothe polarization by the external electric field, etc., are in anequilibrium state and the particles 1512 arranged at a predetermineddistance may act as the photonic crystal. The repulsion due to theelectric charges and the repulsion effect due to the steric hindrancemay be simultaneously exhibited.

In addition, the display device 1500 in accordance with one embodimentof the present invention controls the inter-particle distances of theparticles 1512 by controlling the intensity, direction or AC frequencyof the AC electric field applied through the electrodes 1530 and 1540,thereby controlling the wavelength of light (that is, color) reflectedfrom the particles 1512 (first mode). When the AC voltage is applied,the inter-particle mutual attraction is generated according to theelectrical polarization generated in accordance with the applied ACvoltage and the mutual repulsion is generated by electric chargesequally charged on the surface of the particles or a layer generatingthe inter-particle steric effect, thereby enabling the particles so asto be maintained at a constant distance by the equilibrium of theattraction and the repulsion. Therefore, when the AC voltage is applied,the generated electrical polarization should be applied within thefrequency range that can be sufficiently changed according to thefrequency of the AC voltage.

As described above, since the wavelength of light reflected from theparticles 1512 arranged at a predetermined distance is determined by thedistance of the particles 1512, the distance of the particles 1512 iscontrolled by the intensity and direction of the electric filed appliedthrough the electrode, thereby arbitrarily controlling the wavelength oflight reflected from the particles 1512.

Next, the display device 1500 in accordance with one embodiment of thepresent invention controls the intensity or direction of the DC electricfield applied through the electrodes 1530, 1540 and 1550, such that theintensity of the electric field is a specific threshold value or more,thereby moving the particles 1512 according to the principle of theelectrophoresis or the dielectrophoresis, such that the unique color ofany one of the solutions 1512 and 1514, the particles 1512, the solvent1514 and the lower electrode 1540 may be displayed (second mode).

Referring to FIG. 15(b), as described in detail with reference to theabove second mode, when the electric field is not applied or whenvoltage lower than the threshold value is applied, the particles 1512are irregularly dispersed in the solvent 1514, and thus, the color ofthe solution, in which the unique color of the particles 1512, theunique color of the solvent 1514 and the color of light reflected orscattered from the particles 1512 or the solvent 1514 are mixed, may bedisplayed.

The mutual switching between the photonic crystal reflection mode ofFIG. 15(a) and the solution color reflection mode of FIG. 15(b) may beimplemented by the intensity of applied voltage. That is, the appliedvoltage used in the photonic crystal reflection mode may be larger thanthe applied voltage used in the particle color reflection mode.

Various hues may be represented by the simple method and structure byselectively implementing the photonic crystal reflection mode and thesolution color reflection mode within the same unit pixel. In theembodiment of the switching between the photonic crystal reflection modeand the solution color reflection mode, as shown in FIG. 15, the lowerelectrode may be integrated without being divided.

Referring to FIG. 15(c), as described in detail with reference to thesecond mode, when the particles 1512 have electric charges and theelectric field is applied at the intensity of a threshold value or moreso that the upper electrode 1530 becomes the electrode of a signopposite to the electric charges of the particles 1512, the particles1512 moves toward the upper electrode 1530 by the electrophoresis, andthus, the unique color of the particles 1512 may be displayed on thedisplay unit 1510.

The mutual switching between the photonic crystal reflection mode ofFIG. 15(a) and the particle color reflection mode of FIG. 15(c) may beimplemented by the intensity of applied voltage. That is, the appliedvoltage used in the photonic crystal reflection mode may be smaller thanthe applied voltage used in the particle color reflection mode.Alternatively, the photonic crystal mode of FIG. 15(a) may beimplemented using the AC voltage and FIG. 15(c) may be implemented byapplying the DC voltage. That is, the mode can be switched by changingthe type of voltage (DC or AC).

Various colors may be represented by the simple method and structure byselectively implementing the photonic crystal reflection mode and thesolution color reflection mode within the same unit pixel. In theembodiment of the switching between the photonic crystal reflection modeand the solution color reflection mode, as shown in FIG. 15, the lowerelectrode may be integrated without being divided.

Referring to FIG. 15(d), as described in detail with reference to thesecond mode, when the particles 1512 have electric charges and theelectric field is applied at the intensity of a threshold value or moreso that the lower electrode 1540 becomes the electrode of a signopposite to the electric charges of the particles 1512, the particles1512 moves toward the lower electrode 1540 by the electrophoresis, andthus, the unique color of the solvent 1512 may be displayed on thedisplay unit 1510.

The mutual switching between the photonic crystal reflection mode ofFIG. 15(a) and the solvent color reflection mode of FIG. 15(d) may beimplemented by the intensity of applied voltage. That is, when thecharged particles are applied with an electric field so as to move tothe upper electrode, the photonic crystal reflection mode may beimplemented according to the intensity of the electric filed and whenthe charged particles are applied with an electric field so as to moveto the lower electrode, the solvent color reflection mode may beimplemented.

Various hues may be represented by the simple method and structure byselectively implementing the photonic crystal reflection mode and thesolution color reflection mode within the same unit pixel. In theembodiment of the switching between the photonic crystal reflection modeand the solvent color reflection mode, as shown in FIG. 15, the lowerelectrode may be integrated without being divided.

Referring to FIG. 15(e), as already described in detail with referenceto the second mode, when the particles 1512 have electric charges andthe electric field is applied so that the local electrode 1550 becomesthe electrode of a sign opposite to the electric charges of theparticles 1512, the particles 1512 moves toward the local electrode 1550by the electrophoresis so as to be concentrated around the localelectrode 1550, such that the unique color of the lower electrode 1540(when the lower electrode is transparent, the color of the materialunder the lower electrode) may be displayed on the display unit 1510.

The mutual switching between the photonic crystal reflection mode ofFIG. 15(a) and the electrode color reflection mode of FIG. 15(e) may beimplemented by the region to which the applied voltage is applied. Thatis, although the electric field is uniformly applied in the photoniccrystal reflection mode, the mutual switching may be implemented byapplying the electric field only to the local region of the displayelectrode in the electrode color reflection mode. The intensity of theapplied electric field of the photonic crystal reflection mode may beweaker than that of the electrode color reflection mode.

Various hues may be represented by the simple method and structure byselectively implementing the photonic crystal reflection mode and theelectrode color reflection mode within the same unit pixel. In theembodiment of the switching between the photonic crystal reflection modeand the electrode color reflection mode, as illustrated in FIG. 15, theswitching may be implemented by dividing the upper electrode withoutdividing the lower electrode as illustrated in FIG. 15 and the form ofthe division electrode is not limited to FIG. 15 and therefore, may bediversely implemented and may be applied only to the plurality of localregions.

In particular, as described above, it is difficult to implement whiteand black colors in the first mode. Therefore, the color of thecontinuous hues and white and black may be rendered in the same unitpixel or the same display region by using a combination of the white andblack with the colors of solvent, particle and electrode (in the case ofthe transparent electrode, the color of the material under the lowerelectrode) in the second mode.

Meanwhile, the embodiment of the case in which the first mode and thesecond mode are performed and the embodiment of the case in which anyone of the first mode and the second mode is switched to the other modewithin the same unit pixel will be described below in more detail.

First, the case in which the particles have the electric charges of thesame signal can be assumed. In this case, when the electric field is notapplied or is the threshold voltage or less, the particles areirregularly dispersed in the solvent, and thus, the second mode, inwhich the color of the solvent is displayed, may be performed. Inaddition, when the electric field is the DC electric field and theintensity of the DC electric field is controlled within the range thatcan regularly control the inter-particle distances, the first mode, inwhich the wavelength of light reflected from the particles according tothe intensity of the DC electric field is controlled within the visiblespectrum, may be performed. In addition, when the electric field is theDC electric field and the intensity of the electric field is thethreshold value or more that can concentrate the particles toward theelectrode by the electrophoresis, the second mode, in which theparticles are concentrated on the upper electrode to display the colorof the particles, or concentrated on the lower electrode to display thecolor of the solvent, or concentrated on the local electrode to displaythe colors of the upper electrode or the lower electrode, may beperformed.

In addition, when the electric field is the AC electric field and theintensity and frequency of the AC electric field are controlled withinthe range that can regularly control the inter-particle distances, thefirst mode, in which the wavelength of light reflected from theparticles according to the intensity or frequency of the AC electricfield is controlled within the visible spectrum, may be performed. Whenthe AC voltage is applied, not only the intensity of the AC voltage butalso its frequency can be variables to control the inter-particledistances of the photonic crystal mode. In addition, the photoniccrystal reflection mode may be implemented by applying the AC voltage inthe first mode and may be implemented by applying the DC voltage in thesolvent color reflection mode, the particle color reflection mode andthe electrode color reflection mode among the second mode. In this case,when the solution (particle or solvent or a combination thereof)indicates the electrical polarization characteristic, the photoniccrystal mode implementation can be more facilitated.

Next, the case in which the particles have the electrical polarizationcharacteristic (when the electric field is applied, the electricalpolarization is induced and the electrical polarization is changedaccording to the change in the applied electric field) and includes thestructure generating the steric effect may be assumed. In this case,when the electric field is not applied or is the threshold voltage orless, the particles are irregularly dispersed in the solvent, and thus,the second mode, in which the color of the solvent is displayed, may beperformed. In addition, when the electric field is the DC electric fieldand the intensity of the DC electric field is controlled within therange that can regularly control the inter-particle distances, the firstmode, in which the wavelength of light reflected from the particlesaccording to the intensity of the DC electric field is controlled withinthe visible spectrum, may be performed. In addition, when thedistribution of the electric field is non-uniform and the dielectricconstants of the particles and solvent are different from each other, ifthe DC electric field is applied at the threshold value or more that canconcentrate the particles toward the electrode by the electrophoresis,the particles may be concentrated on the upper electrode to display thecolor of the particles, or concentrated on the lower electrode todisplay the color of the solvent, or concentrated on the localelectrode, and thus, the second mode, in which the colors of the upperelectrode or the lower electrode are displayed, may be performed. Inaddition, when the electric field is the AC electric field and theintensity and frequency of the AC electric field are controlled withinthe range that can regularly control the inter-particle distances, thefirst mode, in which the wavelength of light reflected from theparticles according to the intensity or frequency of the AC electricfield is controlled within the visible spectrum, may be performed.

Although not specifically shown in the drawing, the solution colorreflection mode, the particle color reflection mode, the electrode colorreflection mode or the solvent color reflection mode may be switchedfrom the photonic crystal reflection mode, and further, the solutioncolor reflection mode, the particle color reflection mode, the electrodecolor reflection mode and the solvent color reflection mode may beswitched to one another. The configuration of switching in the secondmode will be described below.

(2) Switching Between First Mode and Third Mode within Same Unit Pixelor Cell

FIG. 16 is a view exemplarily illustrating the configuration of thedisplay device capable of selectively performing the first mode and athird mode in accordance with one embodiment of the present invention.

Referring to FIG. 16, a display device 1600 in accordance with oneembodiment of the present invention may include a display unit 1610 andan electrode. More specifically, the display unit 1610 may includeparticles 1612 that are dispersed in a solvent 1614 and the electrodemay include an upper electrode 1630, a lower electrode 1640 and a localelectrode 1650. In addition, the upper electrode 1630, the lowerelectrode 1640 and the local electrode 1650 may be made of the lighttransmissive material and may transmit light incident on the displaydevice 1600.

In accordance with one embodiment of the present invention, the displaydevice may selectively perform any one of the first mode and the thirdmode so as to be switched to each other. More specifically, anotherdisplay device in accordance with one embodiment of the presentinvention may apply the electric field through the electrode whenparticles are dispersed in the solvent and control at least one of theintensity and direction of the electric field, and thus, may control theinter-particle distances to control the wavelength of light reflectedfrom the photonic crystals composed of particles (first mode) or controlthe distance, location or arrangement of particles to tune thetransmittance of light incident on the display device (third mode).

First, referring to FIG. 16(a), the display device 1600 in accordancewith one embodiment of the present invention controls the inter-particledistances of the particles 1612 by controlling the intensity ordirection of the DC electric field applied through electrodes 1630 and1640, thereby controlling the wavelength of light (that is, color)reflected from the particles 1612 (first mode).

As already described in detail with reference to the first mode, whenthe particles 1612 have the same electric charges, the particles 1612may be regularly arranged at distances where the electrical attractiondue to the external electric field, the electrical repulsion between theparticles 1612 having electric charges of the same sign, and theelectrical attraction due to the polarization by the external electricfield are in an equilibrium state and the particles 1612 arranged at thepredetermined distance may act as the photonic crystal. Meanwhile, whenthe particles 1612 have the steric hindrance capable of causing thesteric hindrance effect, the particles 1612 may be regularly arranged atdistances where the repulsion between the particles due to the stericeffect and the electrical attraction due to the polarization by theexternal electric field, etc., are in an equilibrium state and theparticles 1612 arranged at a predetermined distance may act as thephotonic crystal.

In addition, the display device 1600 in accordance with one embodimentof the present invention controls the inter-particle distances of theparticles 1612 by controlling the intensity, direction or AC frequencyof the AC electric field applied through the electrodes 1630 and 1640,thereby controlling the wavelength of light (that is, color) reflectedfrom the particles 1612 (first mode).

As described above, since the wavelength of light reflected from theparticles 1612 arranged at a predetermined distance is determined by thedistance of the particles 1612, the distance of the particles 1612 iscontrolled by the intensity and direction of the electric filed appliedthrough the electrode, thereby arbitrarily controlling the wavelength oflight reflected from the particles 1612.

Next, the display device 1600 in accordance with one embodiment of thepresent invention control the intensity, direction, application locationof the electric field applied through the electrodes 1630, 1640 and 1650to control the distance, location or arrangement of the particles,thereby tuning the transmittance of light incident on the display device(third mode or transmittance tuning mode).

Referring to FIG. 16(b), as already described in detail with referenceto the third mode, the light in the ultraviolet or infrared spectrum isreflected from the photonic crystals composed of the particles 1612 byapplying the electric field having the intensity of the specificthreshold or more or the specific threshold or less to the photoniccrystals composed of the particles 1612 disposed at a predetermineddistance but the light in the visible spectrum is not reflected, suchthat the light in the visible spectrum incident on the display device1600 may go through the display device 1600 at the high transmittance oflight. This mode may be referred to as the photonic crystaltransmittance tuning mode as described above.

The mutual switching between the photonic crystal reflection mode ofFIG. 16(a) and the photonic crystal transmittance tuning mode of FIG.16(b) may be implemented by the intensity of applied voltage. That is,the applied voltage used in the photonic crystal reflection mode may belarger or smaller than the applied voltage used in the photonic crystaltransmittance tuning mode. The photonic crystal transmittance tuningmode of ultraviolet rays may have the application voltage larger thanthat of the photonic crystal reflection mode and the photonic crystaltransmittance tuning mode of infrared rays is reverse thereto.

Various hues and transmittance may be represented by the simple methodand structure by selectively implementing the photonic crystalreflection mode and the photonic crystal transmittance tuning modewithin the same unit pixel. In the embodiment of the switching betweenthe photonic crystal reflection mode and the photonic crystaltransmittance tuning mode, as shown in FIG. 16, the lower electrode maybe integrated without being divided.

Referring to FIG. 16(c), as already described in detail with referenceto the third mode, when the particles 1612 have electric charges and theelectric field is applied so that the local electrode 1650 becomes theelectrode of a sign opposite to the electric charges of the particles1612, the particles 1612 moves toward the local electrode 1650 by theelectrophoresis so as to be concentrated around the local electrode1650, such that the light incident on the display device 1600 may gothrough the display device 1600 at high transmittance of light withoutbeing reflected or scattered by the particles. Meanwhile, although notshown in the drawing, the transmittance may also be tuned by controllingthe density in which the particles are concentrated on the lower localelectrode. For example, it may also be considered the configuration oftuning the transmittance of light transmitting the particles and/or thesolvent by disposing the local electrode at the central portion of thelower electrode, and then, controlling the density in which theparticles are concentrated on the local electrode. This mode may bereferred to as the particlephoresis transmittance tuning mode in thespecification and may also be implemented by applying the AC voltage andthe DC voltage.

The mutual switching between the photonic crystal reflection mode ofFIG. 16(a) and the particlephoresis transmittance tuning mode of FIG.16(c) may be implemented by the intensity of applied voltage. That is,the applied voltage used in the photonic crystal reflection mode may besmaller than the applied voltage used in the particlephoresistransmittance tuning mode.

As such, various hues may be represented by the simple method andstructure by selectively implementing the photonic crystal reflectionmode and the particlephoresis transmittance tuning mode within the sameunit pixel. In the embodiment of the switching between the photoniccrystal reflection mode and the particlephoresis transmittance tuningmode, as shown in FIG. 16, the lower electrode is not divided but theupper electrode may be divided.

Meanwhile, referring to FIG. 16(d), as already described in detail withreference to the third mode, when the electric field is applied to theparticles 1612 and the solvent 1614 when the particles 1612 having theelectrical polarization characteristic are dispersed in the solvent1614, the particles 1612 are polarized by the electric field to bepolarized in the same direction along the direction of the electricfield. In this case, since the electrical attraction is generatedbetween the particles 1612 polarized in the same direction, theparticles 1612 dispersed in the solvent 1614 are attracted to eachother, such that the particles 1612 may be regularly arranged in adirection parallel to the direction of the electric field. Therefore,the transmittance of light incident on the display device 1600 can betuned by controlling the arrangement state of the particles 1612regularly arranged in a direction parallel to the direction of theelectric field by controlling the intensity or direction of the electricfield. This mode may be referred to as the particle alignment or thearrangement transmittance tuning mode.

The mutual switching between the photonic crystal reflection mode ofFIG. 16(a) and the particle alignment transmittance tuning mode of FIG.16(d) may be implemented by the intensity of applied voltage. That is,in accordance with one embodiment of the present invention, the voltageapplied in the particle alignment transmittance tuning mode may belarger than the voltage applied in the photonic crystal reflection mode.

As such, various hues may be represented by the simple method andstructure by selectively implementing the photonic crystal reflectionmode and the particle alignment transmittance tuning mode within thesame unit pixel. In the embodiment of the switching between the photoniccrystal reflection mode and the particle alignment transmittance tuningmode, as shown in FIG. 16, the lower electrode may be integrated withoutbeing divided.

Meanwhile, the embodiment of the case in which the first mode and thethird mode are performed and the embodiment of the case in which any oneof the first mode and the third mode is switched to the other mode willbe described below in more detail.

First, the case in which the particles have the electric charges of thesame sign and the electrode includes the light transmissive material maybe assumed. In this case, when the electric field is the DC electricfield and the intensity of the DC electric field is controlled withinthe range capable of regularly controlling the inter-particle distances,the first mode, in which the wavelength of light reflected from theparticles according to the intensity of the DC electric field iscontrolled within the visible spectrum, may be performed or the thirdmode, in which the wavelength of light reflected from the particles iscontrolled out of the visible spectrum to tune the transmittance of theincident light, may be performed. In addition, when the electric fieldis the DC electric field and the intensity of the DC electric field isthe threshold value or more capable of concentrating the particlestoward the electrode by the electrophoresis, the third mode, in whichthe particles are concentrated on the local electrode to tune thetransmittance of the incident light, may be performed. In addition, whenthe electric field is the DC electric field and the intensity of the DCelectric field may be controlled within the range capable of arrangingthe particles in a direction parallel to the direction of the DCelectric field, the third mode, in which the particles are arranged inthe state of forming a predetermined angle to the progressing directionof the incident light to tune the transmittance of the incident light,may be performed. In this case, when the electric field is the ACelectric field and the intensity and frequency of the AC electric fieldis controlled within the range capable of regularly controlling theinter-particle distances, the first mode, in which the wavelength oflight reflected from the particles according to the intensity orfrequency of the AC electric field is controlled within the visiblespectrum, may be performed or the third mode, in which the wavelength oflight reflected from the particles is controlled out of the visiblespectrum to tune the transmittance of the incident light, may beperformed. In addition, when the electric field is the AC electric fieldand the intensity and frequency of the AC electric field may becontrolled within the range capable of arranging the particles in adirection parallel to the direction of the AC electric field, the thirdmode, in which the particles are arranged in the state of forming apredetermined angle to the progressing direction of the incident lightto tune the transmittance of the incident light, may be performed. Inone embodiment, when voltage is applied, arranging the magnitude involtage in a large order is as follows; the particlephoresistransmittance tuning mode>the particle alignment transmittance tuningmode>the photonic crystal transmittance tuning mode of ultravioletreflection>the visible photonic crystal reflection mode>the photoniccrystal transmittance tuning mode of infrared reflection. These modesmay be indicated while being mixed with each other. This may mean thattheir exerted effects are changed.

In addition, the AC voltage may be used in the photonic crystalreflection mode, the photonic crystal transmittance tuning mode and theparticle alignment transmittance tuning mode and the DC voltage may beused in the particlephoresis transmittance tuning mode.

Next, another case may be assumed, in which the particles have theelectrical polarization characteristic (when the electric field isapplied, the electrical polarization is induced and the electricalpolarization is changed according to the change in the applied electricfield) and includes the structure generating the steric effect and theelectrode includes the light transmissive material. In this case, whenthe electric field is the DC electric field and the intensity of the DCelectric field is controlled within the range capable of regularlycontrolling the inter-particle distances, the first mode, in which thewavelength of light reflected from the particles according to theintensity of the DC electric field is controlled within the visiblespectrum, may be performed or the third mode, in which the wavelength oflight reflected from the particles is controlled out of the visiblespectrum to tune the transmittance of the incident light, may beperformed. In addition, when the electric field is the DC electric fieldand the intensity of the DC electric field is the threshold value ormore capable of concentrating the particles toward the electrode by thedielectrophoresis, the third mode, in which the transmittance of theincident light by concentrating the particles on the local electrode istuned, may be performed. In addition, when the electric field is the DCelectric field and the intensity of the DC electric field may becontrolled within the range capable of arranging the particles in adirection parallel to the direction of the DC electric field, the thirdmode, in which the particles are arranged in the state of forming apredetermined angle to the progressing direction of the incident lightto tune the transmittance of the incident light, may be performed. Inthis case, when the electric field is the AC electric field and theintensity and frequency of the AC electric field is controlled withinthe range capable of regularly controlling the inter-particle distances,the first mode, in which the wavelength of light reflected from theparticles according to the intensity of the AC electric field iscontrolled within the visible spectrum, may be performed or the thirdmode, in which the wavelength of light reflected from the particles iscontrolled out of the visible spectrum to tune the transmittance of theincident light, may be performed. In addition, when the electric fieldis the AC electric field and the intensity and frequency of the ACelectric field may be controlled within the range capable of arrangingthe particles in a direction parallel to the direction of the ACelectric field, the third mode, in which the particles are arranged inthe state of forming a predetermined angle to the progressing directionof the incident light to tune the transmittance of the incident light,may be performed.

Although not specifically illustrated in the drawing, the particlealignment transmittance tuning mode, the particlephoresis transmittancetuning mode and the photonic crystal transmittance tuning mode may beswitched to one another. The configuration of switching in the thirdmode will be described below.

(3) Switching Between Second Mode and Third Mode within Same Unit Pixelor Cell

FIG. 17 is a view exemplarily illustrating the configuration of thedisplay device capable of selectively performing the second and thirdmodes in accordance with one embodiment of the present invention.

Referring to FIG. 17, a display device 1700 in accordance with oneembodiment of the present invention may include a display unit 1710 andan electrode. More specifically, the display unit 1710 may includeparticles 1712 that are dispersed in a solvent 1714 and the electrodemay include an upper electrode 1730, a lower electrode 1740 and a localelectrode 1750. In addition, the particles 1712 and the solvent 1714included in the display unit 1710 may each have the unique color and allof the upper electrode 1730, the lower electrode 1740 and the localelectrode 1750 may be made of the light transmissive material and maytransmit light incident on the display device 1700.

In accordance with one embodiment of the present invention, the displaydevice may selectively perform any one of the second mode and the thirdmode within the same unit pixel so as to be switched to each other. Morespecifically, another display device in accordance with one embodimentof the present invention may apply the electric field through theelectrode when particles are dispersed in the solvent and control atleast one of the intensity and direction of the electric field, andthus, may control the location of the particles to display the uniquecolor of the solution, particle or solvent (second mode) or control thedistance, location or arrangement of particles to tune the transmittanceof light incident to the display device (third mode).

First, the display device 1700 in accordance with one embodiment of thepresent invention controls the intensity or direction of the DC electricfield applied through the electrodes 1730, 1740 and 1750, such that theintensity of the electric field is a specific threshold value or more,thereby moving the particles 1712 according to the principle of theelectrophoresis or the dielectrophoresis, such that the unique color ofany one of the solutions 1712 and 1714, the particles 1712 and thesolvent 1714 may be displayed (second mode).

Referring to FIG. 17(a), as described in detail with reference to theabove second mode, when the electric field is not applied, the particles1712 is irregularly dispersed in the solvent 1714, and thus, the colorof the solution, in which the unique color of the particles 1712, theunique color of the solvent 1714, and the color of light reflected orscattered from the unique color of the particles 1712 or the solvent1714 are mixed, may be displayed. This mode is the solution colorreflection mode.

Referring to FIG. 17(b), as already described in detail with referenceto the second mode, when the particles 1712 have electric charges andthe electric field is applied so that the upper electrode 1730 becomesthe electrode of a sign opposite to the electric charges of theparticles 1712, the particles 1712 moves toward the upper electrode 1730by the electrophoresis, and thus, the unique color of the particles 1712may be displayed on the display unit 1710. This mode is the particlecolor reflection mode.

Referring to FIG. 17(c), as described in detail with reference to thesecond mode, when the particles 1712 have electric charges and theelectric field is applied so that the lower electrode 1740 becomes theelectrode of a sign opposite to the electric charges of the particles1712, the particles 1712 move toward the lower electrode 1740 by theelectrophoresis, and thus, the unique color of the solvent 1712 may bedisplayed on the display unit 1710. This mode is the solvent colorreflection mode.

Next, the display device 1700 in accordance with one embodiment of thepresent invention control the intensity or direction of the electricfield applied through the electrodes 1730, 1740 and 1750 to control thedistance, location or arrangement of the particles, thereby tuning thetransmittance of light incident to the display device (third mode).

Referring to FIG. 17(d), as already described in detail with referenceto the third mode, the light in the ultraviolet or infrared spectrum isreflected from the photonic crystals composed of the particles 1712 byapplying the electric field having the intensity of the specificthreshold or more or the specific threshold or less to the photoniccrystals composed of the particles 1712 disposed at a predetermineddistance but the light in the visible spectrum is not reflected, suchthat the light in the visible spectrum incident to the display device1700 may go through the display device 1700 at the high transmittance oflight. This mode is the photonic crystal transmittance tuning mode.

Referring to FIG. 17(e), as already described in detail with referenceto the third mode, when the particles 1712 have electric charges and theelectric field is applied so that the local electrode 1750 becomes theelectrode of a sign opposite to the electric charges of the particles1712, the particles 1712 moves toward the local electrode 1750 by theelectrophoresis so as to be concentrated around the local electrode1750, such that the light incident to the display device 1700 may gothrough the display device 1700 at high transmittance of light withoutbeing reflected or scattered by the particles. This mode is theparticlephoresis transmittance tuning mode.

Meanwhile, referring to FIG. 17(f), as already described in detail withreference to the third mode, when the electric field is applied to theparticles 1712 and the solvent 1714 when the particles 1712 having theelectrical polarization characteristic are dispersed in the solvent1714, the particles 1712 are polarized by the electric field to bepolarized in the same direction along the direction of the electricfield. In this case, since the electrical attraction is generatedbetween the particles 1712 polarized in the same direction, theparticles 1712 dispersed in the solvent 1714 are attracted to eachother, such that the particles 1712 may be regularly arranged in adirection parallel to the direction of the electric field. Therefore,the transmittance of light incident on the display device 1700 can betuned by controlling the arrangement state of the particles 1712regularly arranged in a direction parallel to the direction of theelectric field by controlling the intensity or direction of the electricfield. This mode is the particle alignment transmittance tuning mode.

First, referring to the switching between the solution color reflectionmode and the photonic crystal transmittance tuning mode, the magnitudein the applied voltage is large in the photonic crystal transmittancetuning mode and the voltage cannot be applied in the solution colorreflection mode. Both of the hues and the transmittance can becontrolled by using the unit pixel due to the switching between thesolution color reflection mode and the photonic crystal transmittancetuning mode within the same unit pixel.

Next, referring to the switching between the solution color reflectionmode and the particlephoresis transmittance tuning mode, the magnitudein the applied voltage is large in the particlephoresis transmittancetuning mode and the voltage cannot be applied in the solution colorreflection mode. Both of the hues and the transmittance can be tuned byusing the unit pixel due to the switching between the solution colorreflection mode and the particlephoresis transmittance tuning modewithin the same unit pixel.

Next, referring to the switching between the solution color reflectionmode and the particle alignment transmittance tuning mode, the magnitudein the applied voltage is large in the particle alignment transmittancetuning mode and the voltage cannot be applied in the solution colorreflection mode. Both of the hues and the transmittance can be tuned byusing the unit pixel due to the switching between the solution colorreflection mode and the particle alignment transmittance tuning modewithin the same unit pixel.

Next, referring to the switching between the particle color reflectionmode and the photonic crystal transmittance tuning mode, the magnitudein the applied voltage is larger in the particle color reflection modethan in the photonic crystal transmittance tuning mode. Both of the huesand the transmittance can be tuned by using the unit pixel due to theswitching between the particle color reflection mode and the photoniccrystal transmittance tuning mode within the same unit pixel.

Next, referring to the switching between the particle color reflectionmode and the particlephoresis transmittance tuning mode, the magnitudein the applied voltage may be equal to or different from each other, butthe direction of the applied voltage is different. Both of the hues andthe transmittance can be tuned by using the unit pixel due to theswitching between the particle color reflection mode and theparticlephoresis transmittance tuning mode within the same unit pixel.

Next, referring to the switching between the particle color reflectionmode and the particle alignment transmittance tuning mode, the magnitudein the applied voltage is larger in the particle color reflection modethan in the particle alignment transmittance tuning mode. Both of thehues and the transmittance can be tuned by using the unit pixel due tothe switching between the particle color reflection mode and theparticle alignment transmittance tuning mode within the same unit pixel.

Next, referring to the switching between the solution color reflectionmode and the photonic crystal transmittance tuning mode, the magnitudein the applied voltage is larger in the solvent color reflection modethan in the photonic crystal transmittance tuning mode. Both of the huesand the transmittance can be tuned by using the unit pixel due to theswitching between the solvent color reflection mode and the photoniccrystal transmittance tuning mode within the same unit pixel.

Next, referring to the switching between the solvent color reflectionmode and the particlephoresis transmittance tuning mode, the magnitudeand direction in the applied voltage may be the same, but the electrodeapplied with the voltage is different. That is, the voltage is appliedto the large electrode in the solvent color reflection mode, but thevoltage is applied to the small electrode or the local electrode in theparticlephoresis transmittance tuning mode. Meanwhile, when thetransmittance is very small in the particlephoresis transmittance tuningmode, the magnitude in the voltage may be smaller in case of the solventcolor reflection mode. Both of the hues and the transmittance can betuned by using the unit pixel due to the switching between the solventcolor reflection mode and the particlephoresis transmittance tuning modewithin the same unit pixel.

Finally, referring to the switching between the solvent color reflectionmode and the particle alignment transmittance tuning mode, the magnitudein the applied voltage is larger in the solvent color reflection modethan in the particle alignment transmittance tuning mode. Both of thehues and the transmittance can be tuned by using the unit pixel due tothe switching between the solvent color reflection mode and the particlealignment transmittance tuning mode within the same unit pixel.

Meanwhile, the embodiment of the case, in which the second mode and thethird mode are performed and the embodiment of the case in which any oneof the second mode and the third mode is switched to the other mode,will be described below in more detail.

First, it may be assumed the case in which the particles have theelectric charges of the same sign and the electrode includes the lighttransmissive material. In this case, when the electric field is notapplied, the particles are irregularly dispersed in the solvent, andthus, the second mode, in which the color of the solution is displayed,may be performed. In addition, when the electric field is the DCelectric field and the intensity of the DC electric field is controlledwithin the range that can regularly control the inter-particledistances, the third mode, in which the wavelength of light reflectedfrom the particles is controlled within the visible spectrum to tune thetransmittance of the incident light, may be performed. In addition, whenthe electric field is the DC electric field and the intensity of theelectric field is the threshold value or more that can concentrate theparticles toward the electrode by the electrophoresis, the second mode,in which the particles are concentrated on the upper electrode todisplay the color of the particles or concentrated on the lowerelectrode to display the color of the solvent, may be performed or thethird mode, in which the particles are concentrated on the localelectrode to tune the transmittance of the incident light, may beperformed. In addition, when the electric field is the DC electric fieldand the intensity of the DC electric field may be controlled within therange capable of arranging the particles in a direction parallel to thedirection of the AC electric field, the third mode, in which theparticles are arranged in the state of forming a predetermined angle tothe progressing direction of the incident light to tune thetransmittance of the incident light, may be performed. In addition, whenthe electric field is the AC electric field and the intensity andfrequency of the AC electric field are controlled within the range thatcan regularly control the inter-particle distances, the third mode, inwhich the wavelength of light reflected from the particles is controlledout of the visible spectrum to tune the transmittance of the incidentlight, may be performed. In addition, when the electric field is the ACelectric field and the intensity and frequency of the AC electric fieldmay be controlled within the range capable of arranging the particles ina direction parallel to the direction of the AC electric field, thethird mode, in which the particles are arranged in the state of forminga predetermined angle to the progressing direction of the incident lightto tune the transmittance of the incident light, may be performed.

Referring to the magnitude in the voltage in each mode shown in FIG. 17,in one embodiment, when the DC voltage is applied, there may be an orderof the particle color reflection mode=the solvent color reflection modethe particlephoresis transmittance tuning mode>the particle alignmenttransmittance tuning mode>the photonic crystal transmittance tuningmode>the solution color reflection mode. In one embodiment, when the ACvoltage is applied, there may be an order of the particle alignmenttransmittance tuning mode>the photonic crystal transmittance tuningmode>the solution color reflection mode.

Next, another case in which the particles have the electricalpolarization characteristic (when the electric field is applied, theelectrical polarization is induced and the electrical polarization ischanged according to the change in the applied electric field) andincludes the structure that generates the steric effect and theelectrode includes the light transmissive material may be assumed. Inthis case, when the electric field is not applied, the particles areirregularly dispersed in the solvent, and thus, the second mode, inwhich the color of the solution is displayed, may be performed. Inaddition, when the electric field is the DC electric field and theintensity of the DC electric field is controlled within the range thatcan regularly control the inter-particle distances, the third mode, inwhich the wavelength of light reflected from the particles is controlledout of the visible spectrum to tune the transmittance of the incidentlight, may be performed. In addition, when the electric field is the DCelectric field and the intensity of the electric field is the thresholdvalue or more that can concentrate the particles toward the electrode bythe dielectrophoresis, the second mode, in which the particles areconcentrated on the upper electrode to display the color of theparticles or concentrated on the lower electrode to display the color ofthe solvent, may be performed or the third mode, in which the particlesare concentrated on the local electrode to tune the transmittance of theincident light, may be performed. In addition, when the electric fieldis the DC electric field and the intensity of the DC electric field maybe controlled within the range capable of arranging the particles in adirection parallel to the direction of the AC electric field, the thirdmode, in which the particles are arranged in the state of forming apredetermined angle to the progressing direction of the incident lightto tune the transmittance of the incident light, may be performed. Inaddition, when the electric field is the AC electric field and theintensity and frequency of the AC electric field are controlled withinthe range that can regularly control the inter-particle distances, thethird mode, in which the wavelength of light reflected from theparticles is controlled out of the visible spectrum to tune thetransmittance of the incident light, may be performed. In addition, whenthe electric field is the AC electric field and the intensity andfrequency of the AC electric field may be controlled within the rangecapable of arranging the particles in a direction parallel to thedirection of the AC electric field, the third mode, in which theparticles are arranged in the state of forming a predetermined angle tothe progressing direction of the incident light to tune thetransmittance of the incident light, may be performed.

(4) Mode Switching in Second Mode (Unique Color Reflection Mode) withinSame Unit Pixel or Cell

The second mode that is the unique color reflection mode may includefour individual modes, that is, (a) the solution color reflection mode,(b) the particle color reflection mode, (c) the solvent color reflectionmode and (d) the electrode color reflection mode as shown in FIG. 57. Asshown in FIG. 57, the individual sub modes may also be switched to oneanother within the same unit pixel. For example, the DC voltage or veryslight DC voltage may be applied in the solution color reflection mode.Although the same voltage is applied in the particle color reflectionmode, the solvent color reflection mode and the electrode colorreflection mode, the application direction and the application locationmay be different from each other, or different voltage, in which theapplication direction and the application location is changed, may beapplied. That is, voltage is applied to both of the upper electrode andthe lower electrode so that the particles are toward the upper electrodein the particle color reflection mode, voltage is applied to the upperelectrode and the lower electrode so that the particles are toward thelower electrode in the solvent color reflection mode, and voltage isapplied only the upper electrode and the local electrode of the lowerelectrode so that the particles are toward the local electrode of thelower electrode in the electrode color reflection mode. In theembodiment, a total 6 (4*3/2) types of the mode switching can beperformed. The description of each sub mode is described above. Thereby,various hues may be implemented within the same unit pixel.

(5) Mode Switching in Third Mode (Transmittance Tuning Mode) within SameUnit Pixel or Cell

In the third mode that is the transmittance tuning mode, as shown inFIG. 58, a total 3 of individual sub modes may be performed. That is,there are (a) the photonic crystal transmittance tuning mode, (b) theparticlephoresis transmittance tuning mode and (c) the particlealignment transmittance tuning mode. As shown in FIG. 58, the modeswitching between these individual sub modes may also be performed. Forexample, the magnitude in the applied voltage is an order of theparticlephoresis transmittance tuning mode>the particle alignmenttransmittance tuning mode>the photonic crystal transmittance tuningmode. In the embodiment, a total 3 types of mode switching may beperformed, thereby enabling various transmittance tuning.

(6) Switching Among First Mode, Second Mode and Third Mode within SameUnit Pixel or Cell

FIG. 18 is a view exemplarily illustrating the configuration of thedisplay device capable of selectively performing the first, second andthird modes in accordance with one embodiment of the present invention.

Referring to FIG. 18, a display device 1800 in accordance with oneembodiment of the present invention may include a display unit 1810 andan electrode. More specifically, the display unit 1810 may include theparticles 1812 that are dispersed in a solvent 1814 and the electrodemay include an upper electrode 1830, a lower electrode 1840 and a localelectrode 1850. In addition, the particles 1812 and the solvent 1814included in the display unit 1810 may each have the unique color and allof the upper electrode 1830, the lower electrode 1840 and the localelectrode 1850 may be made of the light transmissive material and maytransmit light incident on the display device 1800.

In accordance with one embodiment of the present invention, the displaydevice may selectively perform any one of the first mode, the secondmode and the third mode within the same unit pixel so as to be switchedto each other. More specifically, another display device in accordancewith one embodiment of the present invention may apply the electricfield through the electrode when particles are dispersed in the solventand control at least one of the intensity and direction of the electricfield and thus, and thus, may control the inter-particle distances tocontrol the wavelength of light reflected from the photonic crystalscomposed of particles (first mode), control the location of the particleto display the unique color of the solution, particle or solvent (secondmode), or control the distance, location or arrangement of particles totune the transmittance of light incident to the display device (thirdmode).

First, referring to FIG. 18(a), the display device 1800 in accordancewith one embodiment of the present invention controls the inter-particledistances of the particles 1812 by controlling the intensity ordirection of the DC electric field applied through electrodes 1830 and1840, thereby controlling the wavelength of light (that is, color)reflected from the particles 1812 (first mode).

As described in detail with reference to the first mode, when theparticles 1812 have the same electric charges, the particles 1812 may beregularly arranged at distances where the electrical attraction due tothe external electric field, the electrical repulsion between theparticles 1812 having electric charges of the same sign, and thepolarization due to the external electric field are in an equilibriumstate, and the particles 1812 arranged at the predetermined distance mayact as the photonic crystal. Meanwhile, when the particles 1812 have thesteric hindrance capable of causing the steric hindrance effect, theparticles 1812 may be regularly arranged at distances where therepulsion between the particles due to the steric effect and theelectrical attraction due to the polarization by the external electricfield, etc., are in an equilibrium state, and the particles 1812arranged at a predetermined distance may act as the photonic crystal.

In addition, the display device 1800 in accordance with one embodimentof the present invention controls the inter-particle distances of theparticles 1812 by controlling the intensity, direction or AC frequencyof the AC electric field applied through the electrodes 1830 and 1840,thereby controlling the wavelength of light (that is, color) reflectedfrom the particles 1812 (first mode).

As described above, since the wavelength of light reflected from theparticles 1812 arranged at a predetermined distance is determined by thedistance of the particles 1812, the distance of the particles 1812 iscontrolled by the intensity and direction of the electric filed appliedthrough the electrode, thereby arbitrarily controlling the wavelength oflight reflected from the particles 1812.

First, the display device 1800 in accordance with one embodiment of thepresent invention controls the intensity or direction of the DC electricfield applied through the electrodes 1830, 1840 and 1850, such that theintensity of the electric field is a specific threshold value or more,thereby moving the particles 1812 according to the principle of theelectrophoresis or the dielectrophoresis, such that the unique color ofany one of the solutions 1812 and 1814, the particles 1812 and thesolvent 1814 may be displayed (second mode).

Referring to FIG. 18(b), as described in detail with reference to theabove second mode, when the electric field is not applied, the particles1812 are irregularly dispersed in the solvent 1814, and thus, the colorof the solution, in which the unique color of the particles 1812, theunique color of the solvent 1814 and the color of light reflected orscattered from the unique color of the particles 1812 or the solvent1814 are mixed, may be displayed (solution color reflection mode).

Referring to FIG. 18(c), as described in detail with reference to thesecond mode, when the particles 1812 have electric charges and theelectric field is applied at so that the upper electrode 1830 becomesthe electrode of a sign opposite to the electric charges of theparticles 1812, the particles 1812 moves toward the upper electrode 1830by the electrophoresis, and thus, the unique color of the particles 1812may be displayed on the display unit 1810 (particle color reflectionmode).

Referring to FIG. 18(d), as described in detail with reference to thesecond mode, when the particles 1812 have electric charges and theelectric field is applied so that the lower electrode 1840 becomes theelectrode of a sign opposite to the electric charges of the particles1812, the particles 1812 move toward the lower electrode 1840 by theelectrophoresis, and thus, the unique color of the solvent 1814 may bedisplayed on the display unit 1810 (solvent color reflection mode).

Next, the display device 1800 in accordance with one embodiment of thepresent invention control the intensity or direction of the electricfield applied through the electrodes 1830, 1840 and 1850 to control thedistance, location or arrangement of the particles, thereby tuning thetransmittance of light incident to the display device (third mode).

Referring to FIG. 18(e), as already described in detail with referenceto the third mode, the light in the ultraviolet or infrared spectrum isreflected from the photonic crystals composed of the particles 1812 byapplying the electric field having the intensity of the specificthreshold or more or the specific threshold or less to the photoniccrystals composed of the particles 1812 disposed at a predetermineddistance, but the light in the visible spectrum is not reflected, suchthat the light in the visible spectrum incident to the display device1800 may go through the display device 1800 at the high transmittance oflight (photonic crystal transmittance tuning mode).

Referring to FIG. 18(f), as already described in detail with referenceto the third mode, when the particles 1812 have electric charges and theelectric field is applied so that the local electrode 1850 becomes theelectrode of a sign opposite to the electric charges of the particles1812, the particles 1812 moves toward the local electrode 1850 by theelectrophoresis so as to be concentrated around the local electrode1850, such that the light incident to the display device 1800 may gothrough the display device 1800 at high transmittance of light withoutbeing reflected or scattered by the particles (particlephoresistransmittance tuning mode).

Meanwhile, referring to FIG. 18(g), as already described in detail withreference to the third mode, when the electric field is applied to theparticles 1812 and the solvent 1814 when the particles 1812 having theelectrical polarization characteristic are dispersed in the solvent1814, the particles 1812 are polarized by the electric field to bepolarized in the same direction along the direction of the electricfield. In this case, since the electrical attraction is generatedbetween the particles 1812 polarized in the same direction, theparticles 1812 dispersed in the solvent 1814 are attracted to eachother, such that the particles 1812 may be regularly arranged in adirection parallel to the direction of the electric field. Therefore,the transmittance of light incident on the display device 1800 can betuned by controlling the arrangement state of the particles 1812regularly arranged in a direction parallel to the direction of theelectric field by tuning the intensity or direction of the electricfield (particle alignment transmittance tuning mode).

Referring to FIG. 18, the representative embodiment stepwise performedfrom the first mode to the third mode using the DC electric field willbe described in detail.

In accordance with one embodiment of the present invention, any one ofthe first mode, the second mode and the third mode may be switched tothe other mode by controlling the intensity or direction of the DCelectric field applied to the display unit 1810 through the electrode.

First, when the electric field is not applied (V=0), since the particlesare irregularly dispersed within the display unit 1810, the lightincident on the display unit 1810 may display the color of the solvent,in which the color irregularly scattered or reflected by the particles1812 and the unique colors of the particles and the solvent are mixed(second mode, see FIG. 18(b)).

Next, when the electric field having the intensity within thepredetermined range is applied by increasing the intensity of theelectric field applied to the display unit 1810 (V=V1), the particles1812 within the display unit 1810 are regularly arranged at thepredetermined distance, and thus, the photonic crystals that reflect thelight having the specific wavelength range may be formed, such that thecolor of the specific wavelength range reflected to the photoniccrystals may be displayed on the display unit 1810 (first mode, see FIG.18(a)) and the wavelength range of the reflected light reaches theinfrared or ultraviolet spectrum beyond the visible spectrum as theintensity of the electric field is further increased, and thus, most ofvisible rays are transmitted, such that the transmittance of theincident light may be increased (third mode, see FIG. 18(e)).

Next, when the electric having larger intensity is applied (V=V2), sincethe particles 1812 may be arranged in a direction parallel to thedirection of the electric field, the transmittance of the incident lightmay be tuned so that the transmittance of the incident light isincreased or reduced according to the incident angle of light incidenton the display unit 1810 (third mode, see FIG. 18(g)).

Next, the intensity of the electric field applied to the display unit1810 is further increased, and thus, the particles 1812 within thedisplay unit 1810 may move or be concentrated on the predeterminedlocation adhered to the electrode by the electrophoresis force when theelectric field having the intensity of the predetermined range or moreis applied (V=V3), such that the unique color of the particles 1812 orthe solvent 1814 is displayed on the display unit 1810 (second mode, seeFIGS. 18(c) and (d)), or the transmittance of the incident light may beincreased as the particles 1812 is concentrated on the local electrode1850 (third mode, see FIG. 18(f)).

Further, the embodiment of the case in which the first mode, the secondmode and the third mode are performed and the embodiment of the case inwhich any one of the first mode, the second mode and the third mode isswitched to the other mode will be described below in more detail.

First, it may be assumed the case in which the particles have theelectric charges of the same sign and the electrode includes the lighttransmissive material. In this case, when the electric field is notapplied, the particles are irregularly dispersed in the solvent, andthus, the second mode, in which the color of the solution is displayed,may be performed. Further, when the electric field is the DC electricfield and the intensity of the DC electric field is controlled withinthe range capable of regularly controlling the inter-particle distances,the first mode, in which the wavelength of light reflected from theparticles according to the intensity of the DC electric field iscontrolled within the visible spectrum, may be performed or the thirdmode, in which the wavelength of light reflected from the particles iscontrolled out of the visible spectrum to tune the transmittance of theincident light, may be performed. In addition, when the electric fieldis the DC electric field and the intensity of the electric field is thethreshold value or more that can concentrate the particles toward theelectrode by the electrophoresis, the second mode, in which theparticles are concentrated on the upper electrode to display the colorof the particles or concentrated on the lower electrode to display thecolor of the solvent, may be performed or the third mode, in which theparticles are concentrated on the local electrode to tune thetransmittance of the incident light, may be performed. In addition, whenthe electric field is the DC electric field and the intensity of the DCelectric field may be controlled within the range capable of arrangingthe particles in a direction parallel to the direction of the ACelectric field, the third mode, in which the particles are arranged inthe state of forming a predetermined angle to the progressing directionof the incident light to tune the transmittance of the incident light,may be performed. In this case, when the electric field is the ACelectric field and the intensity and frequency of the AC electric fieldis controlled within the range capable of regularly controlling theinter-particle distances, the first mode, in which the wavelength oflight reflected from the particles according to the intensity of the DCelectric field is controlled within the visible spectrum, may beperformed or the third mode, in which the wavelength of light reflectedfrom the particles is controlled out of the visible spectrum to tune thetransmittance of the incident light, may be performed. In addition, whenthe electric field is the AC electric field and the intensity andfrequency of the AC electric field may be controlled within the rangecapable of arranging the particles in a direction parallel to thedirection of the AC electric field, the third mode, in which theparticles are arranged in the state of forming a predetermined angle tothe progressing direction of the incident light to tune thetransmittance of the incident light, may be performed.

Next, it may be assumed another case in which the particles have theelectrical polarization characteristic (when the electric field isapplied, the electrical polarization is induced and the electricalpolarization is changed according to the change in the applied electricfield) and includes the structure generating the steric effect and theelectrode includes the light transmissive material. In this case, whenthe electric field is not applied, the particles are irregularlydispersed in the solvent, and thus, the second mode, in which the colorof the solution is displayed, may be performed. Further, when theelectric field is the DC electric field and the intensity of the DCelectric field is controlled within the range capable of regularlycontrolling the inter-particle distances, the first mode, in which thewavelength of light reflected from the particles according to theintensity of the DC electric field is controlled within the visiblespectrum, may be performed or the third mode, in which the wavelength oflight reflected from the particles is controlled out of the visiblespectrum to tune the transmittance of the incident light, may beperformed. In addition, when the electric field is the DC electric fieldand the intensity of the electric field is the threshold value or morethat can concentrate the particles toward the electrode by thedielectrophoresis, the second mode, in which the particles areconcentrated on the upper electrode to display the color of theparticles or concentrated on the lower electrode to display the color ofthe solvent, may be performed or the third mode, in which the particlesare concentrated on the local electrode to tune the transmittance of theincident light, may be performed. In addition, when the electric fieldis the DC electric field and the intensity of the DC electric field maybe controlled within the range capable of arranging the particles in adirection parallel to the direction of the AC electric field, the thirdmode, in which the particles are arranged in the state of forming apredetermined angle to the progressing direction of the incident lightto tune the transmittance of the incident light, may be performed. Inthis case, when the electric field is the AC electric field and theintensity of the AC electric field is controlled within the rangecapable of regularly controlling the inter-particle distances, the firstmode, in which the wavelength of light reflected from the particlesaccording to the intensity of the DC electric field is controlled withinthe visible spectrum, may be performed or the third mode, in which thewavelength of light reflected from the particles is controlled out ofthe visible spectrum to tune the transmittance of the incident light,may be performed. In addition, when the electric field is the ACelectric field and the intensity and frequency of the AC electric fieldmay be controlled within the range capable of arranging the particles ina direction parallel to the direction of the AC electric field, thethird mode, in which the particles are arranged in the state of forminga predetermined angle to the progressing direction of the incident lightto tune the transmittance of the incident light, may be performed.

As shown by multiple arrows in FIG. 18, seven modes a to g, that is, thephotonic crystal reflection mode, the solution color reflection mode,the particle color reflection mode, the solvent color reflection mode,the photonic crystal transmittance tuning mode, the particlephoresistransmittance tuning mode and the particle alignment transmittancetuning mode may organically switched to each other if necessary. In theembodiment, a total 7*6/2=21 types of the mode switching can beperformed. Therefore, various hues tuning and various transmittancetuning can be implemented within the same unit pixel of the displayregion.

Control Unit of Display Device

Meanwhile, the display device according to one embodiment of the presentinvention may include a control unit (not shown) that performs afunction of controlling the intensity, direction, type, applicationfrequency, frequency, application time, application location, etc., ofvoltage generating the electric field applied to the particles and thesolvent. More specifically, the control unit in accordance with the oneembodiment of the present invention generates a control signal applyinga predetermined voltage to an electrode applying the electric field tothe particles and the solvent so as to apply the predetermined electricfield to the particles and the solvent and generates a control signalsetting the intensity, direction, type, application frequency,frequency, application time, application location, etc., of voltage soas to control the electric field applied to the particles and thesolvent to be appropriate for each requirement, thereby enabling to beswitched between various modes as described above. According to oneembodiment of the present invention, the control unit may be included inthe display device in a type of an operating system, application programmodules and other program modules and may physically be stored inseveral known storage devices. In addition, the program module may alsobe stored in a remote storage device communicable with the displaydevice. Meanwhile, the program module includes a routine, a subroutine,a program, an object, a component, a data structure, etc., that executesspecific tasks described below in accordance with one embodiment of thepresent invention or executes a specific abstraction data type, but isnot limited thereto.

Machine Readable Storage Medium

The switching process or configuration between the plurality of modesdescribed up to now is stored on the machine readable storage medium andis read and executed by a machine (for example, computer) and may beexecuted by programs including instructions or program codes thatexecute the aforementioned mode switching process. For example, it willbe briefly described a case in which a process of implementing varioushues by a simple photonic crystal reflection mode and tuning thetransmittance by the particle alignment mode so as to be switched toeach other within the unit pixel is executed by a machine. The programmay include first instruction that regularly arranges the inter-particledistances to apply the AC voltage having a magnitude predominantlyreflecting the wavelength of the visible rays and a second instructionthat applies the voltage having a smaller magnitude than the voltage ofthe magnitude to align the particles and control the predominantlytransmitted light amount. The machine readable storage medium mayinclude any mechanism storing or transmitting information in a type thatcan be read by the machine (for example, computer). For example, themachine readable storage medium may include a ROM, a RAM, a magneticdisk storage medium, an optical storage medium, a flash memory device, asignal transferred in an electrical type, a signal transferred in anoptical type, a signal transferred in an acoustic type or a signaltransferred in other types (for example, a carrier, an infrared signal,a digital signal, an interface transmitting and receiving a signal,etc.), etc.

Various Application Embodiments of Display Device

FIG. 19 is a view exemplarily illustrating the configuration of thedisplay device driven by a plurality of electrodes in accordance withone embodiment of the present invention.

Referring to FIG. 19, electrodes 1922, 1924, 1926 and 1928 in accordancewith one embodiment of the present invention may include a plurality ofelectrodes 1922, 1924, 1926 and 1928 that are capable of independentlyapplying an electric field only to partial regions of a display unit1910 in order to control the distance, location and arrangement of theparticles 1912 included in the display unit 1910 more precisely andindependently. The plurality of electrodes 1922, 1924, 1926 and 1928 canbe individually controlled by a fine driving circuit, such as a thinfilm transistor (TFT). In addition, in accordance with one embodiment ofthe present invention, the electrodes 1922, 1924, 1926 and 1928 may bemade of a light transmissive material so as not to obstruct theprogression of the light emitted from the display unit 1910. Forinstance, the electrodes 1922, 1924, 1926 and 1928 may be made of indiumtin oxide (ITO), titanium oxide (TiO₂), carbon nano tubes and otherelectrically conductive polymer films, etc.

Referring to FIG. 19, the electrodes 1922, 1924, 1926 and 1928 mayinclude a first electrode 1922, a second electrode 1924, a thirdelectrode 1926 and a fourth electrode 1928. First, because no electricfiled is applied to a space covered by the first electrode 1922 to whichno voltage is applied, the particles 1912 located in the space coveredby the first electrode 1922 may be irregularly arranged. Therefore, thedisplay unit 1910 controlled by the first electrode 1922 may notrepresent a color of a solution (second mode). Next, because electricfields corresponding to respective voltages are applied to spacescovered by the second electrode 1924, third electrode 1926 and fourthelectrode 1928 to which voltages of different levels are applied, theparticles 1912 located in the spaces covered by these electrodes may becontrolled in different patterns different from each other whileelectrical attraction induced by the electric fields (i.e., a force thatcauses electrophoresis), electrical repulsion between the particles 1912having electric charges of the same sign and electrical attractioninduced by the polarization (or its increase) of the particles 1912 orsolvent 1914, etc., are in equilibrium. Accordingly, the display unit1910 controlled by the second electrode 1924, third electrode 1926 andfourth electrode 1928 implement different modes according to thecorresponding region, thereby displaying different colors. For instance,under the assumption that a voltage applied to the fourth electrode 1928is greater than a voltage applied to the third electrode 1926, theparticles 1912 located in the space covered by the fourth electrode 1228is concentrated at the location closed to the upper electrode. On theother hand, the particles 1912 located in the space covered by the thirdelectrode 1926 may be regularly arranged at the predetermined distances.Accordingly, the display unit 1910 controlled by the fourth electrode1928 displays the unique color of the particles 1912 and the displayunit 1910 controlled by the third electrode 1926 may reflect the lightin the specific wavelength range reflected from the photonic crystalscomposed of the particles 1912.

FIG. 20 is a view illustrating a configuration in which the particlesand solvent included in the display device are encapsulated in aplurality of capsules in accordance with one embodiment of the presentinvention.

Referring to FIG. 20, particles 2012 and solvent 2014 included in adisplay device 2000 in accordance with one embodiment of the presentinvention may be encapsulated in capsules 2032, 2034, 2036 and 2038 madeof a light transmissive insulating material. By encapsulating theparticles 2012 and the solvent 2014 as shown in FIG. 20, directinterference, such as incorporation, between the particles 2012 andsolvent 2014 included in different capsules can be prevented; theparticles can be prevented from being irregularly arranged due toelectrohydrodynamic (EHD) motion of the particles having electriccharges; the film processibility of the display device 2000 can beimproved by making sealing of the particles and solvent easier; and thedistance, position and arrangement contained in the display device 2000can be independently controlled for each capsule.

Referring to FIG. 20, the display device 2000 in accordance with oneembodiment of the present invention may include four capsules 2032,2034, 2036 and 2038. A first voltage, second voltage, third voltage andfourth voltage can be respectively applied to electrodes 2022, 2024,2026 and 2028 located in the portions of the first capsule 2032, secondcapsule 2034, third capsule 2036 and fourth capsule 2038. Accordingly,the respective capsules, to which electric fields of differentintensities and different directions are applied, reflect light ofdifferent wavelength ranges. As such, with the display device 2000 inaccordance with one embodiment of the present invention, an independentdisplay can be implemented for each capsule.

Unlike FIG. 20, if the electrodes and the capsules are not disposed in acorresponding way to each other and instead, a region covered byelectrodes is smaller than a capsule or one capsule is covered by two ormore electrodes, an independent display can be implemented as desiredfor a given region of the display unit by using an electrode pattern.That is, in accordance with one embodiment of the present invention,when an electric field is applied to a specific region in a capsulethrough one of the plurality of electrodes that covers the capsule, onlythe solvent and/or particles existing in the specific region among theparticles existing in the capsule reacts with the electric field, butthe particles and/or solvent existing in other regions does not reactwith the electric field. Thus, a region (i.e., display region) on whichlight of a specific wavelength is reflected can be determined by anelectrode pattern, rather than by the size or pattern of the capsules.

FIG. 21 is a view illustrating a configuration in which particles andsolvent included in the display device are dispersed in a medium inaccordance with one embodiment of the present invention.

Referring to FIG. 21, the particles and solvent included in a displaydevice 2100 in accordance with one embodiment of the present inventionmay be dispersed in a medium 2130 made of a light transmissive material.More specifically, a predetermined amount of particles and solvent maybe dispersed and distributed in the form of droplets in the lighttransmissive insulating material 2130 which does not change in responseto external stimuli such as an electric field, thus partially isolatingthe particles contained in the display device 2100. That is, inaccordance with one embodiment of the present invention, the solventwith the particles dispersed therein is dispersed and distributed in thelight transmissive medium 2130 to prevent the occurrence of directinterference, such as incorporation, between the particles or solventincluded in different regions to thereby control the inter-particledistances contained in the display device 2100 more independently.

Referring to FIG. 21, the display device 2100 in accordance with oneembodiment of the present invention may include a plurality of regions2112 and 2114 included in the medium 2130. More specifically, thedistance, location and arrangement of the particles contained in a firstregion 2110 located in between the first electrodes 2142 to which afirst voltage is applied and the distance, location and arrangement ofthe particles contained in the second region 2120 located in betweensecond electrodes 2144 to which a second voltage is applied can becontrolled independently from each other. Therefore, the first region2110 and the second region 2120 can display different colors.Accordingly, with the display device 2100 in accordance with oneembodiment of the present invention, an independent display can beimplemented for each region. In FIG. 21, since the voltage appliedthrough the upper and lower electrodes drops by a light transmissiveinsulation medium 2130 and may not be uniform, the solution dispersed inthe light transmissive medium may contact the upper and lower electrodesor may be uniformly distributed in the light transmissive medium.

FIG. 22 is a view exemplarily illustrating a composition of a solutionencapsulated with a light transmissive medium in accordance with oneembodiment of the present invention. For reference, FIG. 22 correspondsto a photograph taken by an electron microscope on a cross-section ofthe display device 2100 mentioned with reference to FIG. 21.

Referring to FIG. 22, it can be seen that the solvent with the particles2210 dispersed therein is encapsulated in a light transmissiveinsulating material which does not flow by an electric field. Inaccordance with one embodiment of the present invention, the solution(i.e., mixture of the particles and solvent) with the particles 2210dispersed in the solvent in a colloidal state is mixed with a differentkind of immiscible solution to form an emulsion, and then, the emulsioninterface is coated with the light transmissive material 2220, therebybeing encapsulated in the light transmissive material 2220. Here, anoxidized steel (FeOx) cluster coated with a charge layer may be used asthe particles, a solvent having electrical polarization characteristicmay be used as the solvent, and a light transmissive polymer materialcontaining gelatin may be used as the capsule material.

FIG. 23 is a view illustrating the composition of the particles andsolvent dispersed in a medium in accordance with one embodiment of thepresent invention. For reference, FIG. 23 corresponds to a photographtaken by an electron microscope on a cross-section of the display device1600 mentioned with reference to FIG. 21.

Referring to FIG. 23, it can be seen that the solvent 2320 with theparticles 2310 dispersed therein is dispersed in a medium 2330 made oflight transmissive material of a solid or gel state which does notchange in response to external stimuli, such as an electric field, amagnetic field, etc. In accordance with one embodiment of the presentinvention, the particles 2310 having electric charges are dispersed inthe solvent 2320 and the resultant dispersion are evenly mixed in thelight transmissive medium 2330 in the form of droplets, therebyobtaining the composition shown in FIG. 23. Moreover, in accordance withone embodiment of the present invention, in FIG. 23, the particles 2310may be an oxidized steel (FeO_(x)) cluster coated with a charge layer,the solvent 2320 may be ethylene glycol (EG), and the medium 2330 may bepolydimethylsiloxane (PDMS).

FIG. 24 is a view illustrating a configuration in which the particlesand solvent included in the display device are partitioned into aplurality of cells in accordance with one embodiment of the presentinvention.

Referring to FIG. 24, the particles 2412 and solvent 2414 included inthe display device 2400 in accordance with one embodiment of the presentinvention can be isolated by partition walls etc., made of an insulatingmaterial and partitioned into cells 2432, 2434, 2436 and 2438. Inaccordance the embodiment of the present invention, by partitioning theparticles 2412 and the solvent 2414, direct interference, such asincorporation, between the particles 2412 and the solvent 2414 to beincluded in different cells can be prevented from occurring.Accordingly, the distance, location, arrangement of the particlescontained in the display device 2400 can be independently controlled foreach cell, and the arrangement state of particles due to the motion ofthe electrohydrodynamic (EHD) of the particles having the electriccharges can be prevented from being irregularly arranged.

Meanwhile, unlike in FIG. 24, even if the electrodes and the cells arenot disposed in a corresponding manner to each other but instead aregion covered by electrodes is smaller than a cell or one cell iscovered by two or more electrodes, an independent display can beimplemented as desired for an any region of the display unit by using anelectrode pattern. That is, according to one embodiment of the presentinvention, when an electric field is applied to a specific region in acell through one of the plurality of electrodes that cover the cell,only the solvent and/or particles existing in the specific region amongthe particles existing in the cell reacts with the electric field, butthe particles and/or solvent existing in other regions does not reactwith the electric field. Thus, a region (i.e., display region) on whichlight of a specific wavelength is reflected can be determined by anelectrode pattern, rather than by the size or pattern of the cells.

Meanwhile, in order to manufacture a structure shown in FIG. 24, thepartition walls are first manufactured on the lower substrate by methodssuch as screen printing, gravure printing, lithography, etc., and then,may be manufactured by filling the solution, in which the particles aredispersed, such as one drop filling (ODF), etc.

Further, as the partition walls for dividing the solution in FIG. 24,the empty space other than the insulating material in the solid form maybe used. That is, the solution may be partitioned by not dispersing theparticles in a region in which the affinity with the solution is low bydividing the region in which the affinity with the solution is locallyhigh and low due to the patterning of the substrate. For example, whenthe solution is hydrophilic, the partition wall portion is manufacturedto have liphophilic characteristic by patterning the substrate and theregion into which the solution will be permeated is manufactured to haveliphophilic characteristic, such that the solution may be filled only inthe hydrophilic portion and may be partitioned by the liphophilicregion. Further, when the lower substrate is liphophilic and the lowerelectrode is hydrophilic, the cell partition may be simultaneouslyperformed by the patterning of the lower electrode.

As described above, when encapsulating the particles and the solvent inaccordance with one embodiment of the present invention or dispersing orpartitioning the particles and the solvent in the medium, theinter-particle distance, location and arrangement of particles can beindependently controlled for each capsule, each region or each cell,thereby more precisely implementing the display and facilitating themaintenance and repair of the display device.

FIGS. 25 and 26 are views exemplarily illustrating a configuration inwhich the display device in accordance with one embodiment of thepresent invention is combined with each other in a vertical direction ora horizontal direction.

Referring first to FIG. 25, particles 2512 and a solvent 2514 includedin a display device 2500 in accordance with one embodiment of thepresent invention may be included in each of the plurality of cells2532, 2534 and 2536 that are coupled (that is, stacked) with each otherin a vertical direction, thereby independently controlling the distance,location and arrangement of the particles included in the display device2400 for each cell. Therefore, when the electrode 2520 located among theplurality of cells 2532, 2534 and 2536 that are stacked with one anotheris made of the light transmissive material, the color due to each modeindependently implemented in the plurality of stacked cells 2532, 2534and 2536 may be displayed by being mixed with each other. For example,the first mode may be implemented in the first cell 2532 to control thecolor of the reflected light, the second mode may be implemented in thesecond cell 2534 to display the unique color of the particles 2512, andthe third mode may be implemented in the third cell 2536 to tune thetransmittance of light. Therefore, the mixing of more various colors maybe implemented and the transmittance and the hue may be combined to beappropriate to requirements.

Next, referring to FIG. 26, particles 2612 and a solvent 2614 includedin a display device 2600 in accordance with one embodiment of thepresent invention may be included in each of the plurality of cells2632, 2634 and 2636 that are coupled with each other in a horizontaldirection, thereby independently controlling the distance, location andarrangement of the particles included in the display device 2400 foreach cell. Therefore, the color or the transmittance of light of eachmode implemented in each of the plurality of cells 2632, 2634 and 2636coupled with each other may be shown while being mixed with one another.For example, the first mode may be implemented in the first cell 2632 tocontrol the color of the reflected light, the second mode may beimplemented in the second cell 2634 to display the unique color of theparticles 2612, and the third mode may be implemented in the third cell2636 to tune the transmittance of light.

Meanwhile, although the embodiments of FIGS. 19 to 26 have beendescribed with respect to the case where both of the upper and lowerelectrodes are divided into a plurality of electrodes, either one of theupper and lower electrodes may be formed as a common electrode. Forinstance, in the actual application to display products, the upperelectrode may be formed as a common electrode made of a transparentelectrode material, while the lower electrode may be divided into unitcells and connected to a transistor for driving each cell and may not bemade of a transparent electrode material. Further, the transparent upperelectrode is used and the particles and the voltage of the same sign asthe charged electric charges are applied to the lower electrode, suchthat the charged particles are arranged on the upper electrode, therebyminimizing the phenomenon that the intensity of light is attenuated bythe solvent.

FIGS. 27 to 29 are views illustrating a pattern of voltages applied tothe display device in accordance with one embodiment of the presentinvention.

First, referring to FIG. 27, the display device in accordance with oneembodiment of the present invention may further include a control unit(not shown) that performs the function of resetting the inter-particledistances at times between the intervals of changing of the intensityand/or direction of an electric field when sequentially applyingelectric fields of different intensities and/or different directions tothe dispersion including the particles, and thus, achieving a continuousdisplay. More specifically, when sequentially applying a first voltageand a second voltage using the electrode applying the electric field tothe particles and solvent, the control unit in accordance with oneembodiment of the present invention performs the function of bringingthe particles, which are arranged at predetermined distance, positionand arrangement by the first voltage, back to the initial or reset stateby applying a reset voltage having the opposite polarity to the firstvoltage to the particles and solvent before applying the second voltageafter the application of the first voltage. With this, the displaydevice in accordance with one embodiment of the present invention canimprove display performance, including improving the operating speed andsuppressing afterimages. Moreover, according to one embodiment of thepresent invention, the reset voltage is applied with the oppositepolarity to the just previously applied voltage. Therefore, according toone embodiment of the present invention, even when the display device isturned off, the operating speed can be raised by forcibly moving theparticles, which are moved and arranged in a predetermined direction bythe just previously applied voltage, into the opposite direction.

Next, referring to FIG. 28, the display device in accordance with oneembodiment of the present invention may further include a control unit(not shown) that performs the function of maintaining the inter-particledistances at predetermined distance, location or arrangement in advanceto be a predetermined distance, location or arrangement whensequentially applying electric fields of different intensities anddifferent directions to the particles and solvent and achieving acontinuous display. More specifically, when sequentially applying afirst voltage and a second voltage to the electrode applying theelectric field to the particles and solvent, the control unit inaccordance with one embodiment of the present invention performs thefunction of rapidly adjusting the distance, location or arrangement ofthe particles to the desired distance, location or arrangement byapplying a predetermined standby voltage in advance and then applyingthe first voltage or the second voltage. With this, the display devicein accordance with one embodiment of the present invention can improvedisplay performance, including increased response speed and fasterscreen change. For instance, in the conventional electronic papertechnology, particles of a specific color had to be moved to run throughfrom one end to the opposite end in a cell in order to display aparticular color. In contrast, in the present invention, photoniccrystals can be realized in a manner that a standby voltage having arelatively low level enough not to make reflected light in a visiblespectrum appear is applied so as to concentrate the particles on oneside in the cell, and then, a voltage of a specific level or greater isapplied to reflect light in the visible spectrum. Hence, the photoniccrystals for reflecting light in the visible spectrum can be realizedjust by moving the particles slightly, thereby making the operatingspeed of such a display device faster.

Subsequently, referring to FIG. 29, the display device in accordancewith one embodiment of the present invention may further include acontrol unit (not shown) that performs the function of applying anelectric field of various patterns of the intensity, duration ofapplication, etc., of the electric field when sequentially applyingelectric fields of different intensities and/or different directions tothe particles and solvent and achieving a continuous display. Morespecifically, when applying a voltage to the electrode applying theelectric field to the particles and solvent, the control unit inaccordance with one embodiment of the present invention can increase ordecrease the level of a voltage to a predetermined voltage (see 29(a),can extend or reduce the duration or period of application of a certainvoltage (see 29(b)), and can obtain the same effect as continuousapplication of a voltage by repeatedly applying a discontinuous pulsevoltage (see 29(c)). By doing so, the display device in accordance withone embodiment of the present invention can improve display performance,including enabling display of various patterns and reducing powerconsumption.

It should be noted, however, that the electric field application patternin accordance with the present invention is not necessarily limited tothose listed above, but may be appropriately changed within the scope ofthe objects of the present invention, i.e., within the scope in whichthe distance, location or arrangement of particles can be controlled byan electric field.

FIG. 30 is a view exemplarily illustrating a configuration of a circuitconnected to a plurality of electrodes of the display device inaccordance with one embodiment of the present invention.

Referring to FIG. 30, each of the plurality of electrodes 3020 includedin the display device in accordance with one embodiment of the presentinvention may be connected with the capacitors 3050 capable of storingpredetermined electric charges. In more detail, when the voltage isapplied to the electrode 3020 so as to apply the electric field to thedisplay unit, the capacitor 3050 connected with the correspondingelectrode 3020 may be charged with the electric charges, and thus, thevoltage may be applied to the corresponding electrode 3020 for thepredetermined time by using the electric charges charged in thecapacitor 3050 even after the voltage applied to the correspondingelectrode 3020 is interrupted. Therefore, although the discontinuouspulse voltage is applied to the display device, one embodiment of thepresent invention can implement the same display as the case in whichthe continuous voltage is applied. Therefore, the power consumed tooperate the display device can be reduced and more stable display can beimplemented. In addition, although the applied voltage is interrupted,the display state may be maintained for the predetermined time. That is,the distance, arrangement and location of the particles may bemaintained at the specific distance, the specific arrangement and thespecific location for the predetermined time.

Meanwhile, one embodiment of the present invention can control thebrightness of color displayed on the display device by using the lighttuning layer that controls the pattern (application region, applicationtime, etc.) of the electric field applied to the particles or tunes thetransmittance of light or blocking rate of light reflected from theparticle.

FIG. 31 is a view exemplarily illustrating a configuration ofcontrolling a display area of light reflected from particles inaccordance with one embodiment of the present invention.

Referring to FIG. 31, a display device 3100 in accordance with oneembodiment of the present invention may include nine unit cells 3110,wherein each unit cell 3110 may be independently controlled from eachother by the electric field independently applied to each unit cell3110. Lower electrodes 3122, 3124 and 3126 covering each unit cell 3110may include materials having dark colors or may be covered by a colorlayer (not shown) having dark colors. In accordance with one embodimentof the present invention, in order to display the color of the desiredbrightness on the display device 3100, the color by the photoniccrystals is displayed in a part of the unit cells by applying theappropriate electric field only to some of the total of nine unit cells3110. On the other hand, the color by the photonic crystals is notdisplayed in the remaining unit cell by not applying the electric fieldto the remaining unit cells but the dark color due to the scatteringcolor by the particles or the color of the lower electrode may bedisplayed. Further, when the number of unit cells displaying the colorby the photonic crystals by controlling the electric field applied toeach unit cell is increased, since the area in which the color isdisplayed by the photonic crystals is wider than the area in which thedark color is displayed, the brightness of color by the photoniccrystals is increased, and when the number of unit cells in which thecolor by the photonic crystals is displayed is reduced, since the darkcolor is displayed is narrower than the area in which the area in whichthe color by the photonic crystals is displayed, the brightness of colorby the photonic crystals may be lowered. That is, as the number of unitcells to which the predetermined electric field capable of forming thephotonic crystals is increased, the number of unit cells in which thecolor by the photonic crystals is displayed, that is, the area in whichthe color by the photonic crystals is displayed is increased, therebyincreasing the brightness. In addition, the brightness may be controlledby using the lower electrode as the black electrode and appropriatelycombining the number of pixels implementing the photonic crystalsreflection mode and the number of pixels implementing the transmittancetuning control mode.

FIG. 32 is a view exemplarily illustrating a configuration ofcontrolling a display time of light reflected from particles inaccordance with one embodiment of the present invention.

Referring to FIG. 32, the display device in accordance with oneembodiment of the present invention can control the time when theelectric field is applied to the particles and may include a lowerelectrode, which has a material of a dark color or is covered by a colorlayer (not shown) of the dark color. The display device in accordancewith one embodiment of the present invention can periodically apply theelectric field to the particles but can control the ratio of theapplication time of the electric field to the non-application time ofthe electric field so as to display the color of the desired brightnesson the display device. More specifically, if the application time of theelectric field is longer than the non-application time of the electricfield, since the time when the color by the photonic crystals isdisplayed is longer than the time when the dark color is displayed, thebrightness of color by the photonic color may become high. On the otherhand, if the application time of the electric field is shorter than thenon-application time of the electric field, since the time when thecolor by the photonic crystals is displayed is shorter than the timewhen the dark color is displayed, the brightness of color by thephotonic color may become low. That is, as the time when the electricfield capable of forming the predetermined photonic crystals is appliedis long, the time when the color by the photonic crystals is displayedis increased. Therefore, the brightness of color by the photoniccrystals is increased.

FIG. 33 is a view exemplarily illustrating a configuration ofcontrolling brightness using a light tuning layer in accordance with oneembodiment of the present invention.

Referring to FIG. 33, a display device 3300 in accordance with oneembodiment of the present invention may include a separate light tuninglayer 3330 capable of tuning the transmittance of light or lightblocking rate. Generally, since the transmittance of light or the lightblocking rate may greatly affect the intensity or brightness of light,and further, may change the brightness of color of light, the lighttuning layer 3330 capable of tuning the transmittance of light or thelight blocking rate may be disposed on the top of the display device3300. Herein, the brightness of color of light displayed on the displaydevice 3300 may be controlled by controlling the intensity or brightnessincident on the light tuning layer 3330. Hereinafter, various componentscapable of being controlled as the light tuning layer 3330 will bedescribed in detail.

FIGS. 34 and 35 are views exemplarily illustrating a configuration ofthe light tuning layer tuning the transmittance of light in accordancewith one embodiment of the present invention.

First, referring to FIG. 34, a light tuning layer 3400 in accordancewith one embodiment of the present invention may tune the transmittanceof light by controlling the arrangement of particles 3410. Morespecifically, when the electrophoresis particles 3410 are irregularlydispersed within the light tuning layer 3400, the transmittance of lightis reduced due to the reflection or scattering of light by theelectrophoresis particles 3410, and thus, the brightness of color oflight is reduced (see FIG. 34(a)). On the other hand, when theelectrophoresis particles 3410 are regularly arranged in a directionparallel to a progressing direction of light, the progressing of lightis little hindered, and thus, the transmittance of light is high, suchthat the brightness of color of light is increased (see FIG. 34(b)). Inaddition, although not shown, as described above, the layer of using thephotonic crystal transmittance tuning mode may be used as the lighttuning layer.

Next, referring to FIG. 35, a light tuning layer 3500 in accordance withone embodiment of the present invention may tune the transmittance oflight by controlling the location of electrophoresis particles 3510.More specifically, when the electrophoresis particles 3510 areirregularly dispersed within the light tuning layer 3500, thetransmittance of light is reduced due to the reflection or scattering oflight by the electrophoresis particles 3510, and thus, the brightness ofcolor of light is reduced (see FIG. 35(a)). On the other hand, when theelectrophoresis particles 3510 moves toward a lower electrode 3550having a narrow area, the progressing of light is little hindered, andthus, the transmittance of light is high, such that the brightness ofcolor of light is increased (see FIG. 35(b)).

FIG. 36 is a view exemplarily illustrating a configuration of the lighttuning layer controlling a light blocking rate in accordance with oneembodiment of the present invention.

Referring to FIG. 36, a light tuning layer 3600 in accordance with thepresent invention may include a light blocking material 3615 whosedistribution area may be changed as liphophilic or hydrophiliccharacteristics are changed by the electric field. The light blockingmaterial 3615 controls an area covering the display region, that is, thedisplay unit (not shown) of the display device by controlling at leastone of the intensity and direction of the electric field applied to thelight blocking material 3615, thereby controlling the light blockingrate (electro-wetting). More specifically, when the light blockingmaterial 3615 covers most of the display region, the light blocking rateis increased, and thus, the brightness of color of light is reduced (seeFIG. 36(a)), but when the light blocking material 3615 covers a portionof the display region, the light blocking rate is reduced, and thus, thebrightness of color of light is increased (see FIG. 36(b)).

However, the light tuning layer that may be applied to the displaydevice in accordance with the present invention is not necessarilylimited to the above list and various units such as the device ofcontrolling the concentration of the particles may be applied as thelight tuning layer in accordance with the present invention. The devicecapable of changing the transmittance of light according to the voltagesuch as a liquid crystal, the device capable of tuning the transmittanceof light by changing an area of the solution on the surface by changingthe hydrophilic/liphophilic characteristics according to voltage, or thedevice of tuning the transmittance of light by controlling motion of theparticles according to the voltage, etc., may be used. In addition,electrochromic devices (ED), suspended particle devices (SPD), polymerdispersed liquid crystal devices (PDLL), micro-blinds (MB), etc., may beapplied as the light tuning layer.

Meanwhile, in accordance with one embodiment of the present invention, acolor representing an achromatic color and a cell representing achromatic color are spatially and temporally combined, therebycontrolling the chroma of color displayed on the display device.

First, similar to the brightness control method shown in FIG. 31, thechroma of color displayed on the display device may be controlled bycontrolling an area in which the achromatic color is displayed and anarea in which the chromatic color is displayed. More specifically, whenthe number of unit cells displaying the chromatic color is increased bycontrolling the electric field applied to each unit cell, since the areain which the chromatic color is displayed is wider than the area inwhich the achromatic color is displayed, the chroma of the colordisplayed on the display device is increased and when the number of unitcells displaying the achromatic color is reduced, since the area inwhich the chromatic color is displayed is narrower than the area inwhich the achromatic color is displayed, the chroma of the colordisplayed on the display device may be reduced.

Next, similar to the brightness control method shown in FIG. 32, thechroma of color displayed on the display device may be controlled bycontrolling the time when the achromatic color is displayed and the timewhen the chromatic color is displayed. More specifically, if the timewhen the electric field is applied so as to display a chromatic color islonger than the time when the electric field is applied so as to displaythe achromatic color, the chroma of the color displayed on the displaydevice is increased. On the other hand, if the time when the electricfield displaying the chromatic color is applied is shorter than the timewhen the electric field displaying the achromatic color is not applied,the chroma of the color displayed on the display device is reduced.

FIG. 37 is a view illustrating the configuration of a display device forrealizing a photonic crystal display using particles having differentelectric charges from each other in accordance with one embodiment ofthe present invention.

First, the case of the first mode will be described as follows. First,referring to FIG. 37, a display unit 3710 of a display device 3700 inaccordance with one embodiment of the present invention may includeparticles having different electric charges, i.e., one type of particles3712 having negative charges and the other type of particles 3714 havingpositive charges. As an electric field is applied to the display unit3710, the particles 3712 having negative charges and the particles 3714having positive charges may be respectively moved in the oppositedirection and regularly arranged. For instance, if an upper electrode3720 of the electric field generating and/or applying unit is a positiveelectrode and a lower electrode 3725 thereof is a negative electrode,the particles 3712 having negative charges and the particles 3714 havingpositive charges may be moved in the upper electrode 3720 direction andin the lower electrode 3725 direction, respectively, and arranged asphotonic crystals while maintaining predetermined inter-particledistances. In this case, the display device 3700 can reflect light of acertain wavelength range against both sides (i.e., the side of the upperelectrode 3720 and the side of the lower electrode 3725), and thus, canrealize a double-sided display. Furthermore, if the charge amount of theparticles 3712 having negative charges and the charge amount of theparticles 3714 having positive charges are different from each other, asan electric field is applied, the inter-particle distances 3712 havingnegative charges and the inter-particle distances 3714 having positivecharges may differ from each other. Thus, the display device 3700 canreflect light of different wavelength ranges against both sides, andthus, can realize a display, both sides of which are controlledindependently from each other.

Next, the case of the second mode will be described as follows. Theparticles 3712 having negative charges and particles 3714 havingpositive charges that are included in the display device 3700 may havetheir unique colors. In this case, similar to the case of FIG. 37,different colors can be displayed on the upper and lower parts of thedisplay device just by adjusting only the direction of an electric fieldapplied to the upper electrode 3720 and the lower electrode 3725. Forinstance, assuming that the particles 3712 having negative charges arein black and the particles 3714 having positive charges are in white,when a positive voltage is applied to the upper electrode 3720, theblack particles 3712 having negative charges may be moved toward theupper electrode 3720 to display black on the upper part of the displaydevice. When a negative voltage is applied to the upper electrode 3720,the white particles 3714 having positive charges may be moved toward theupper electrode 3720 to display white on the upper part of the displaydevice.

As shown in FIG. 37, the first mode and the second mode may also beswitched to each other in the both-sided display device. In addition,when the lower electrode is divided into the large electrode and thelocal electrode, the first mode, the second mode and the third mode maybe switched to one another in the both-sided display device.

FIGS. 38 to 40 are views exemplarily illustrating a configuration ofpatterning an electrode in accordance with one embodiment of the presentinvention.

First, referring to FIG. 38, a lattice-shaped insulating layer 3830 canbe formed on the lower electrode 3825 (or upper electrode 3820) of theelectrode in accordance with one embodiment of the present invention,and thus, the lower electrode 3825 (or upper electrode 3820) can bepatterned at predetermined intervals.

In accordance with the display device shown in FIG. 38, the patterninginterval of the electrodes is set approximately from several μm toseveral hundreds of μm, thereby preventing the particles from beingirregularly arranged due to electrohydrodynamic (EHD) motion of theparticles having electric charges, and thus, achieving uniform display.In particular, in accordance with the display device shown in FIG. 38,the particles can be effectively prevented from being biased byelectrohydrodynamic motion without passing through a complicatedprocess, such as encapsulation or cell partitioning, which requires alot of time and cost.

Next, referring to FIG. 39, the lower electrode (or upper electrode) inaccordance with one embodiment of the present invention may be dividedinto two electrodes (a first electrode 3920 and a second electrode3925). More specifically, referring to FIG. 40, according to oneembodiment of the present invention, the first electrode 4020 and secondelectrode 4025 constituting the lower electrode (or upper electrode) ofthe electrode can be patterned in the form of alternating teeth.

In accordance with the display device shown in FIGS. 39 and 40, it canbe advantageous in terms of cost saving because electrodes can be formedonly on one substrate, and the operating speed of the display device canbe raised because the moving distance of the particles induced byapplication of an electric field is reduced.

It should be noted, however, that an electrode pattern in accordancewith the present invention is not necessarily limited to those listedabove, but may be appropriately changed within the scope of the objectsof the present invention, i.e., within the scope in which theinter-particle distances can be controlled by an electric field.

FIG. 41 is a view exemplarily illustrating the configuration in whichthe display device in accordance with one embodiment of the presentinvention includes a spacer.

Referring to FIG. 41, a display device 4100 in accordance with oneembodiment of the present invention may include a spacer particles 4130that is disposed between two electrodes 4120 to perform a function ofcontrolling an interval between two electrodes 4120. More specifically,the spacer particles 4130 contacting the upper and lower electrodes 4120may adhere to the upper and lower electrodes 4120 by energy such as heatenergy, photo energy, etc., and thus, may be manufactured in a film typein which the upper and lower electrodes 4130 are disposed at apredetermined distance. In accordance with one embodiment of the presentinvention, the spacer particles 4130 may be made of organic matters suchas polystyrene or inorganic matters such as oxide silicon. When the ITOglass is used as the electrode, the cost is high. Therefore, when thespacer is applied to the substrate in the flexible film type on whichthe transparent electrode is coated as in the present invention, themanufacturing costs may be remarkably reduced.

In accordance with one embodiment of the present invention, a liquid inwhich the particles are dispersed is applied to the front surface usinga device such as one drop filling (ODF) or may be filled between theupper and lower electrodes by using an air pressure difference or may beprinted by a method such as gravure offset, etc.

FIG. 42 is a view illustrating the configuration of a display deviceincluding a solar cell unit in accordance with one embodiment of thepresent invention.

Referring to FIG. 42, a display device 4200 in accordance with oneembodiment of the present invention may further include a solar cellunit 4230 that performs the function of generating an electromotiveforce by using light transmitted through the display device 4200 andstoring it. The electromotive force generated by the solar cell unit4230 can be used to generate and apply a voltage using the electrode4220, whereby the display device 4200 can realize the above-describedphotonic crystal display without depending on an external power supply.However, a combination of the display device and the solar cell unit inaccordance with the present invention is not necessarily limited tothose listed above, but the electromotive force generated by the solarcell unit may be used for other purposes than driving the displaydevice.

FIG. 43 is a view exemplarily illustrating a configuration in which thedisplay device in accordance with the present invention is combined withan emissive display device.

Referring to FIG. 43, separate emissive display devices 4330 and 4340may be combined with the display devices 4310 and 4320 in accordancewith the present invention. More specifically, the emissive displaydevices 4330 and 4340 are combined on the bottom portions of the displaydevices 4310 and 4320 in accordance with the present invention toindependently drive the reflection-type display devices 4310 and 4320and the emissive devices 4330 and 4340 from each other, therebydisplaying the color according to the first, second or third modes inaccordance with one embodiment of the present invention when the displaydevices 4310 and 4320 are operated in accordance with the presentinvention. On the other hand, when the light-emitting display devices4330 and 4340 are operated, light generated from a predetermined backlight and transmitting a color filter may be displayed. That is, theemissive mode and the reflection type mode may be mixed with each other.Reference numeral 4320 represents an R, G and B color filter. In theemissive mode, the particles in the reflection type device move to thelocal electrode to make the transmittance large. When the display devicein accordance with the present invention is combined with the emissivedisplay device, the range of the displayable color can be wide ascompared with the case of using only the display device in accordancewith the present invention. Meanwhile, when the emissive display deviceincludes fluorescent substance, the hues that cannot be implemented bythe existing fluorescent substance may also be implemented. In addition,although not shown in the drawings, the external light source exists onthe upper electrode, such that the reflection type display mode may beimplemented even in the dark situation in which no surrounding light is.

Mode Maintain

In accordance with one embodiment of the present invention, even afterthe electric field acting to control the inter-particle distances isblocked, the inter-particle distances may be maintained in thecontrolled state. To this end, the predetermined additives may beincluded in the solvent in which the particles are dispersed.

More specifically, in accordance with one embodiment of the presentinvention, a polymer type material with a complicated molecularstructure such as a dispersant (for example, polyoxyethylene laurylether, etc.) with a portion (anchoring group, hereinafter, referred toas “anchor”) having strong affinity, a polysorbate-based dispersant (forexample, polyoxyethylene sorbitan monolaurate, polyoxyethylenesorbitanmonooleate, polyoxyethylene sorbitan monostearate, etc.) with at leastone anchor may be added as additives. Accordingly, the motion of theparticles dispersed in the solvent is limited by the additives.

In addition, in accordance with one embodiment of the present invention,when the particles having electric charges are dispersed in the solventto which the polymer having the molecular chain is added, resistance isincreased upon moving the particles in the solvent, such that thelocation may be fixed even after the electric field applied from theoutside is blocked.

In addition, in accordance with one embodiment of the present invention,additives having a functional group (—OH) existing on the surface of theparticles and a functional group (hydrophilic group) that can bechemically bonded such as hydrogen binding are added within the solventso as to make the additives to be continuously adsorbed on the surfaceof the particles, such that the film is formed around the particles,thereby stabilizing the particles.

In addition, in accordance with one embodiment of the present invention,as the steric effect is generated by alkyl component existing in thealkyl chain of the liphophilic group included in the additives addedwithin the solvent, the viscosity of the solvent may be increased,thereby limiting the motion of the particles included in the solvent.Further, a large amount of polymer having the complicated structure isadded within the solvent, thereby further increasing the viscosity ofthe solution.

That is, the additives having the affinity with the particles and theadditives having the affinity with the solvent are added, therebylimiting the motion of the particles within the solvent. In addition,the polymer having the complicated steric structure or chain structureis added within the solvent as the additives, thereby limiting themovement of the particles due to the complicated structure of theadditives.

Meanwhile, the phase change material is used as the solvent, and thus,the inter-particle distances are controlled to have a predetermineddistance by applying voltage in the state of facilitating the movementof the particles (for example, a liquid having low viscosity). Further,before the external voltage is blocked, a state of a solution isconverted into a state of making the movement of the particles hardthrough stimuli such as light, pressure, temperature, chemical reaction,magnetic field, electricity, etc., such that the inter-particledistances of the particles may be maintained constantly although theexternal voltage is blocked.

Alternatively, in order to prevent the inter-particle distances frombeing gradually disordered after voltage is blocked, the inter-particledistances may be maintained at the predetermined distance by aperiodical refreshing with the predetermined voltage.

In order to constantly maintain the distance even after the voltage isblocked by the above-mentioned method, it is preferable to minimize thespecific gravity of the particles and the solvent, such that materialshaving different specific gravity are coated on the particles ormaterials having different specific gravity may be added to the solvent.

Therefore, in accordance with one embodiment of the present invention,the particles regularly arranged while maintaining the predetermineddistance according to the electric field may maintain the regulararrangement although the electric field is blocked. The effect may beapparently shown as the amount of additives is large or the molecularweight of additives is large. In particular, the above effects may beincreased by reducing the difference in the specific gravity between theparticles and the solvent. In addition, in accordance with oneembodiment of the present invention, the display device having theexcellent display characteristics may be manufactured by simplyincluding the additives in the solvent without adopting the complicatedconfiguration such as capsule, cell, droplet type capsule, etc.

In addition, in accordance with one embodiment of the present invention,the configuration in which the polymer stabilizer is covalently bondedwith the particles can be considered. The polymer stabilizer and theparticles have the complementary chemical functionality with each otherso as to forming the covalent binding. The polymer stabilizer may beadded within the solvent.

In addition, in accordance with one embodiment of the present invention,the particles are coated with polymer and the polymer coating includesthe first functional group. In addition, the polymer having the secondfunctional group is added within the solvent and the second functionalgroup acts to apply attraction to the first functional group, such thatthe polymer within the solvent may form a complex with the particles.

Even after the electric field is blocked, the hues continue to bemaintained on the display unit, such that the power consumption is smalland the hues of a frame or an exterior may continue to be stably andreliably maintained.

Meanwhile, in accordance with one embodiment of the present invention,the particles that include a net structure, in which a gel-type solutionis included in the functional group, and are dispersed in the gel-typesolution and include the functional group are considered. However, theconfiguration in which the functional group of the particles and thefunctional group having the net structure are bonded with each other maybe considered.

In one embodiment, the functional group of the gel-state solution or thefunctional group configuring the particles may include at least one ofhydroxyl group (—OH), carboxy group (—COOH), amine group (—NH2), amidgroup (CONH), formyl group (—CHO), tirol group (—SH) and acrylic group(—CH2CCOR).

In one embodiment, the gel-state solution may include aqueous polymer ofat least one of polyvinylalcohols, agaroses, poly(N-isopropylacrylamide)s, polysaccharides, polyamides and polyacrylates.

In one embodiment, the gel-state solution may include monomer or polymerincluding a liphophile and a reactive functional group that have a longchain within a molecule such as 12-hydroxystearic acid, sorbitan esters(Sorbitan monostearate, sorbitan monooleate, etc.), polysorbates(polyoxyethylene sorbitan monooleate, etc.).

In one embodiment, the gel functional group of the solution and thefunctional group of the particles may be bonded with each other by across-linking agent having a bifunctional group including at least oneof boric acid, dialdehydes, dicarboxylic acids, dianhydrides, acidchloride, epichlorohydrin and hydrazide.

In one embodiment, the binding between the functional group of thesurface of the particles and the functional group included in thesolution may be performed by applying the heat energy or the photoenergy or adding the additives or the cross-linking agent.

In one embodiment, the gel-state solution may be phase-changed into thesol state by applying the heat energy or the photo energy or adding theadditive or the cross-linking agent.

Experimental Results

First, the experimental results implementing the first mode inaccordance with one embodiment of the present invention will bedescribed with reference to FIGS. 44 to 51.

FIGS. 44 to 46 are graphs and photographs illustrating experimentalresults implementing the first mode controlling the wavelength of lightreflected photonic crystals composed of the particles by controlling theinter-particle distances when the particles having electric charges aredispersed in a solvent having electrical polarization characteristic inaccordance with one embodiment of the present invention. For reference,in the experiment of FIGS. 44 to 46, particles having a size of 100 to200 nm, charged with negative charges and coated with a silicon oxidefilm were used as the particles having electric charges, a solventhaving a polarity index greater than 1 was used as the solvent havingelectrical polarization characteristic. The intensity of a voltageapplied to apply an electric field to the particles and solvent was setvariously in the range of 0 to 10 V. Meanwhile, the graphs shown in FIG.44 illustrate the reflectance of light reflected from the particlesaccording to the wavelength of the corresponding light when electricfields of various intensities are applied. From FIG. 44, it can be seenthat the greater the degree of change in the wavelength pattern ofreflected light with change in the intensity of an electric field, thelarger the change in the inter-particle distances. This means that lightof more various wavelengths can be reflected from the particles bycontrolling the intensity of the electric field.

Referring to FIG. 44, it can be seen that a wavelength pattern of lightreflected from particles varies variously depends on the intensity of anapplied electric field (i.e., intensity of a voltage). Morespecifically, it can be seen that, the higher the intensity of anapplied electric field (i.e., intensity of a voltage), the shorter thewavelength (in particular, a wavelength in which the reflectance ismaximum) of the light reflected from the particles. According to theexperiment result of FIG. 44, it can be seen that as the intensity(i.e., intensity of a voltage) of an applied electric field isincreased, the color of light reflected from the particles is changedfrom a red series to a blue series and the changeable wavelength rangemay also be wide so as to cover all the visible spectra. Referring toFIGS. 45 and 46, the change in the color of the reflected light asdescribed above may be more visually confirmed in a CIE diagram (FIG.45) and a camera photograph (FIG. 46).

FIGS. 47 and 48 are graphs illustrating the wavelength of lightreflected from the particles as a result of performing an experimentimplementing the first mode by applying an electric field when theparticles having electric charges are dispersed in various solventshaving different polarity indices in accordance with one embodiment ofthe present invention. For reference, in the experiment of FIGS. 47 and48, particles having a size of 100 to 200 nm, charged with negativecharges and coated with a silicon oxide film were used as the particleshaving electric charges, and solvents having polarity indices in thevicinity of 0, 2, 4 and 5 were used as the solvent having electricalpolarization characteristic. More specifically, the graphs (a), (b), (c)and (d) of FIG. 47 illustrate experimental results for the solventshaving polarity indices of 0, 2, 4 and 5, respectively, and the graphs(a), (b), (c) and (d) of FIG. 48 illustrate experimental results for asolvent obtained by mixing a solvent having a polarity index of 0 and asolvent having a polarity index of 4 at ratios of 90:10, 75:25, 50:50and 0:100, respectively. Meanwhile, the graphs shown in FIGS. 47 and 48illustrate the reflectance of the light reflected from the particles inthe wavelength range of a visible light spectrum when electric fields ofvarious intensities are applied. The greater the degree of change in thewavelength pattern of reflected light with change in the intensity of anelectric field, the larger the change in the inter-particle distances.This means that light of more various wavelengths can be reflected fromthe particles by controlling the intensity of the electric field.

Referring to FIG. 47, from graph (a) showing the experimental result forthe solvent having a polarity index of 0, it can be seen that a changein the intensity of an electric field (i.e., intensity of a voltage)causes almost no change in the wavelength pattern of reflected lightbetween the different voltages. It can be seen that the higher thepolarity index (i.e., as the experimental results proceed toward graph(d) from graph (a)), the greater the change in the wavelength pattern ofreflected light with changes in the intensity of an electric field(i.e., intensity of a voltage). Further, referring to FIG. 48, it can beseen that, the higher the ratio of the solvent having a high polarityindex (i.e., as the experimental results proceed toward graph (d) fromgraph (a)), the greater the changes in the wavelength pattern ofreflected light with changes in the intensity of the electric field(i.e., intensity of a voltage).

From the experimental results discussed above, it can be seen that, withthe display device in accordance with one embodiment of the presentinvention, photonic crystals capable of reflecting light of a certainwavelength can be realized in the first mode by properly adjusting thecharge amount and/or polarization amount of the particles, thepolarization amount of the solvent and/or the intensity of an appliedelectric field, and accordingly a display of a certain wavelength range(full spectrum) can be realized.

Next, FIGS. 49 and 50 are graphs and photographs illustrating lightreflected from the particles as a result of performing an experimentimplementing the first mode by applying an electric field when theparticles having electric charges and the electrical polarizationcharacteristic are dispersed in solvents having different polarityindices in accordance with one embodiment of the present invention. Forreference, in the experiment of FIGS. 49 and 50, SrTiO₃ particles (see49(a)) and BaTiO₃ particles (see 34(b)), both of which are charged withelectric charges, were used as the particles having electric charges andelectrical polarization characteristic, and the particles were dispersedin a solvent having a polarity index of 0.

Referring to FIG. 49, it can be seen that the higher the intensity of anelectric field applied to the particles and solvent, the lower thereflectance of light on the whole. From this experimental result, it canbe concluded that upon application of an electric field, the particlesdispersed in the solvent can be electrically polarized and arranged inthe direction of the electric field (see FIG. 50(b)), and thisarrangement leads to a decrease in the number of particles capable ofreflecting incident light and reduces the reflectance of light. Althoughthis experiment does not involve a sharp change in the wavelength ofreflected light with using a configuration in which an electric field isapplied when particles having electrical polarization characteristic aredispersed in a nonpolar solvent, it was found that the particles arearranged in a constant direction as the electric field is applied. Fromthis, it can be seen that the wavelength of the reflected light may alsobe changed by optimizing conditions such as the electric charges on thesurface of the particles.

FIG. 51 is a view illustrating results performing experiments fordependency (that is, the viewing angle of the display device) of anobservation angle of the display device according to the embodiment ofthe present invention.

Referring to FIG. 51(a), although the viewing angle of the displaydevice according to the embodiment of the present invention is changedfrom 20° to 70°, it can be seen that color patterns 5110 to 5160 of thereflected light is little changed. The photonic crystal display deviceaccording to the related art has a disadvantage in that the change inthe color patterns is greatly shown according to the viewing angle.However, it can be seen that the display device in accordance with thepresent invention has an advantage in that the color patterns isconstantly shown without almost any change. It is understood that thisadvantage derives from the fact that the photonic crystals formed by thedisplay device in accordance with the present invention are quasicrystals having a short range order. Accordingly, the display device inaccordance with the present invention can greatly improve displayperformance in comparison with the conventional display device whichmerely forms photonic crystals having a long range order. As shown inthe drawings, in accordance with one embodiment of the presentinvention, when the viewing angle is change between 20° and 70°, thereflected light is changed within 5% of an x value and a y value in CIExy chromaticity coordinates. Further, in accordance with one embodimentof the present invention, the reason why the short range order isgenerated is that the electric field is generated by applying the DCvoltage. By doing so, the particles are regularly arranged bythree-dimensionally arranging the short range order. Thereby, moreexcellent viewing angle characteristics than the display device havingthe long range order can be generally obtained. In addition, in order tomake the viewing angle characteristics excellent, it is preferable toform the electric field by applying the DC voltage or applying the ACvoltage including the DC voltage component. Further, referring to FIG.51(b), in the case of the general photonic crystals according to therelated art, the wavelength of the reflected light is greatly changedaccording to the change in the viewing angle (5170), but in the case ofthe embodiment of the present invention, it can be seen that thewavelength of the reflected light is little changed although the viewingangle is changed (5180 and 5190).

Next, the experimental results implementing the display deviceselectively switching any one of the first, second and third modes inaccordance with one embodiment of the present invention will bedescribed with reference to FIGS. 52 to 57.

FIG. 52 is a view illustrating experimental results of the displaydevice capable of selectively switching any one of the first and secondmodes in accordance with one embodiment of the present invention. Forreference, in the experiment of FIG. 52, the solution having red as theunique color due to the mixing of the particles and the solvent is usedand the intensity of the applied electric field is increased stepwise.

Referring to FIG. 52, when the electric field is not applied, theparticles are irregularly dispersed in the solvent to display the redthat is the unique color of the solution (second mode, see FIG. 52(a))and if the inter-particle distances are controlled due to theapplication of the electric field to form the photonic crystal, the redthat is the unique color of the solution and the color of lightreflected from the photonic crystals are displayed (first mode, see FIG.52(b)), such that it can be seen that the mixed color of the uniquecolor of the solution and the photonic crystal color is displayed (firstmode, see FIGS. 52(c) and 52(d)).

FIGS. 53 and 54 are views illustrating experimental results of thedisplay device capable of selectively switching any one of the first andthird modes in accordance with one embodiment of the present invention.For reference, in the experiment of FIGS. 53 and 54, the transparentsolvent showing the electrical polarization characteristic andtransmitting the light in the visible spectrum, the particles chargedwith the same electric charges and the transparent electrode were used,and the intensity of the applied electric filed was increased stepwise.In addition, in order to confirm the change in transmittance, thespecific patterns are formed under the lower electrode to observewhether the specific patterns are displayed through the display unit.Referring to FIG. 53, when the intensity of the electric field isrelatively small, it can be seen that the light in the visible spectrumis reflected from the photonic crystals made of the particles whosedistances are controlled, and thus, the blue color is displayed on thedisplay device (first mode, see FIGS. 53(a) and 53(b)). However, if theintensity of an electric field is relatively high, it can be seen thatthe blue color displayed on the display device became noticeably lighteras the wavelength range of light reflected by photonic crystals isgradually shifted from the visible spectrum to the ultraviolet spectrum(first mode, see FIG. 53(C)). If the intensity of an electric fieldbecomes much higher, it can be seen that the display device turns into atransparent state while displaying no color as the wavelength range oflight reflected by photonic crystals is completely out of the visiblespectrum, such that the light transmittance becomes high (third mode,see FIGS. 53(d) and 53(e)).

FIG. 54 shows that the reflectance is measured by dispersing theferroelectric particles, which are charged with the same electriccharges and indicate the electrical polarization, in the transparentsolvent indicating the electrical polarization and then applying theelectric field from the outside. When the electric field is not appliedfrom the outside, the solution color 5410 is shown but when the electricrange in the predetermined range is applied from the outside, thephotonic crystal color 5420 is shown by the arrangement of theparticles, and when the larger electric field is applied, the reflectedlight of the photonic crystals is switched into the ultraviolet regionand the inter-particle arrangement effect is shown more larger in thedirection of the electric field, such that the reflected light (increasein the transmitted light) is gradually reduced (5430). That is, theattraction effect due to the electrical polarization is shown largerthan the repulsion due to the same electric charges between theparticles in the case of the predetermined range or more, such that theparticle arrangement effect may be more predominantly shown.

FIGS. 55A, 55B, 55C and 56 are views illustrating experimental resultsof the display device capable of selectively switching any one of thesecond and third modes in accordance with one embodiment of the presentinvention. In FIGS. 55A, 55B, 55C and 56, after the ferroelectricparticles, which are charged with the same sign and have the largeelectrical polarization effect, are dispersed in the light transmissivesolvent and are then filled between the transparent upper and lowerelectrodes having a height of 50 μm, and then, the change degree of thelight transmitting the solution according to the application of theexternal voltage and the reflected light (FIGS. 55A, 55B and 55C) andthe region displayed on the upper electrode were measured by a camera(FIG. 56). For reference, in FIGS. 55A, 55B and 55C, the upper and lowertransparent electrodes were used at the time of measuring thetransmitted light and the reflected light was measured by disposing theblack color plate on the lower electrode at the time of measurement. Inthe experiment of FIG. 56, the unique color patterns including variouscolors from red to blue in a lattice form were disposed on the bottom ofthe transparent lower electrode, the intensity of the applied electricfield is increased stepwise, and the patterns displayed on the upperelectrode was measured by the camera.

Referring to FIG. 55A, it can be seen that the transmittance of light isgradually increased as the intensity of the electric field is increasedfrom 0V to 10V, which shows a process of continuously and variouslyswitching from the second mode, in which the color of the solution isdisplayed, to the third mode, in which the transmittance of light iscontrolled. As can be appreciated from FIG. 55B, the transmittance maybe gradually changed as the intensity of the electric field isincreased. FIG. 55C shows the change in the transmittance and thereflectance according to the applied voltage. From this, when thevoltage of 5V is applied, it can be seen that the change width ofreflectance is 16% (25%−9%) and the change width in transmittance ischanged to 60% (67%−7%) and the operating speed is 1 sec or less. Whenthe transmittance or the reflectance is used, it can be seen that it maybe used as the device displaying the information, such as e-Book. Whenbeing used as the information display device, the white solution coloris displayed if the electric field is not applied and when the electricfield is applied, the black lower electrode is displayed, or conversely,when the black solution and the white lower electrode are used, theinformation may be effectively displayed.

FIG. 59 is a graph illustrating a relation among a wavelength,application voltage and reflectance for implementing the mode and themode switching. In the whole specification of the present invention,implementing the particles dispersed in the solvent at the predeterminedinterval or the specific arrangement is affected by the equilibrium offorce applied between the particles. In particular, when the electricalpolarization of the particles or the solvent is changed according to theexternal electric field, the electrical polarization attractionaffecting between the particles is changed by the induced electricalpolarization and the behavior of the particles is affected according tothe size of the inter-particle repulsion.

First, in the embodiment of the present invention, when theinter-particle repulsion (coulomb repulsion due to the charge coating ofthe same sign or the repulsion due to the steric effect) is applied atthe equivalent intensity to the maximum attraction due to the electricalpolarization induced according to the application of the electric fieldwithin the operating range, the inter-particle distances are constantlymaintained by the equilibrium between the attraction due to theinter-particle electrical polarization according to the application ofthe electric field within the operating range and the above-mentionedinter-particle repulsion, and thus, the specific reflected light isshown and the wavelength of the reflected light is continuously changedtoward the short wavelength as the applied voltage is increased (FIG.59(a)).

In another embodiment of the present invention, when the inter-particlerepulsion of the particles is smaller than the induced electricalpolarization at the threshold voltage or more, the inter-particlerepulsion of particles and the induced electrical polarizationattraction according to the application of the electric field are in anequilibrium state up to the threshold voltage, and the reflected lightis changed. However, in case of the threshold voltage or more, theelectrical polarization attraction is applied stronger than therepulsion, such that the particles may be arranged in the direction ofthe electric field but the inter-particle distances is not controlled atthe specific distance. Therefore, the phenomenon that the reflectedlight is not changed but the transmittance is increased (the reductionin reflection) as shown in FIG. 59(b) may be shown.

Further, when the inter-particle repulsion of the particles isrelatively smaller than the electrical polarization attraction accordingto the application of the electric field, the phenomenon that theparticles are arranged in a chain form in the direction of the electricfield according to the electrical polarization attraction inducedaccording to the application of the electric field as shown in FIG.59(c) is predominantly shown, such that the phenomenon that only theintensity of reflectance rather than the wavelength of the reflectanceis reduced (increase in transmittance) may be shown.

As set forth above, the exemplary embodiments of the present inventioncan implement various hues or continuous hues and the transmittancewithin the same single pixel by the simple structure. In addition, theexemplary embodiments of the present invention can tune various hues,the transmittance, the chroma and/or brightness by the simple structure.Further, the exemplary embodiments of the present invention canimplement the hues of the continuous wavelength by reflecting the lightof the continuous wavelength rather than implementing the hues by themixing of R, G and B. Also, the display method according to theexemplary embodiment of the present invention can simultaneously satisfythe large area display, the simple display method, the continuous hueimplementation, the use in the flexible display region and the displayof the low power consumption. Moreover, with the display device inaccordance with the present invention, various and precise displays canbe realized by independently controlling the particles having electriccharges and the effect of making the maintenance and repair of thedisplay device easier can be achieved. In particular, as compared withthe existing displays, such as an electronic ink, which can only displaya specific color and requires the use of a separate color filter todisplay a color different from the specific color, the display device inaccordance with the present invention is efficient in that it canrealize a display for effectively displaying a structural color over thefull wavelength range without the use of a separate color filter.

Although the above embodiments have been described focusing on thedisplay device using photonic crystal characteristics, the configurationof the present invention is applicable in various fields, includingcolor changing glass, color changing wallpapers, color changing solarcells, color changing sensors, color changing papers, color changingink, anti-counterfeit tags, and so on. For example, using this concept,it is possible to manufacture a portable biosensor capable of detectinga chemical reaction without expensive measurement equipment byconverting a chemical signal obtained from the chemical reaction into anelectric signal and displaying the electric signal in a certain hue.Also, if a material whose phase can be changed by light, heat, pressure,etc., is used as the solvent used for the display device of the presentinvention, electronic paper, electronic ink, etc., that reflect acertain color in a stable and fixed manner can be realized. Moreover, byincorporating a material, such as a fluorescent material or quantum dot(QD) material, into the particles or solvent contained in the displaydevice in accordance with the present invention, a display usingphotonic crystals may be realized in a bright environment, and a displayusing fluorescent material or quantum dots may be realized in a darkenvironment or ultraviolet environment.

Hereinabove, although the present invention is described by specificmatters such as concrete components, etc., exemplary embodiments anddrawings, they are provided only for assisting in the entireunderstanding of the present invention. Therefore, the present inventionis not limited to the exemplary embodiments. Various modifications andchanges may be made by those skilled in the art to which the presentinvention pertains from this description.

While the invention has been shown and described with respect to theparticular embodiments, it will be understood by those skilled in theart that various changes and modification may be made without departingfrom the spirit and scope of the invention as defined in the followingclaims.

1. (canceled)
 2. A display method applying an electric field through anelectrode to a display unit including a solution, in which particles aredispersed in the solvent, and controlling at least one of intensity,direction, application frequency, application time and applicationlocation of the electric field to control at least one of interval,location and arrangement of the particles, wherein the display method isimplemented to selectively switch, within a same pixel of the displayunit, between a first mode for controlling a wavelength of lightreflected from the particles whose distances are controlled bycontrolling inter-particle distances; and a second mode for tuningtransmittance of light transmitting the solution by controlling thedistance, location or arrangement of the particles. 3-13. (canceled) 14.The method of claim 1, wherein at least one of the particles, solventand solution has a variable electrical polarization characteristic,which is a characteristic that an amount of electrical polarizationinduced according to the change of the applied electric field ischanged. 15-26. (canceled)
 27. The method of claim 1, wherein theparticles and the solvent are encapsulated by a light transmissivematerial or are partitioned by an insulating material. 28-30. (canceled)31. The method of claim 1, wherein a unit pixel, in which the switchingbetween the modes is performed, is vertically stacked in a plural numberand the modes are independently implemented within each stacked unitpixel. 32-37. (canceled)
 38. The method of claim 1, wherein energy isgenerated using light incident to the particles and the solvent, and theelectric field is applied by using the generated energy.
 39. The methodof claim 1, wherein an emissive display unit or a transmissive displayunit is used by being combined with the mode.
 40. The method of claim 1,wherein the light reflected from the particles, the solvent or theelectrode or the light transmitting the particles, the solvent or theelectrode is displayed through a color filter connected to theelectrode. 41-52. (canceled)